Part of this answer does have to do with a philosophy of science that is, I think, fairly reasonably guided by our present scientific understanding.

(nb. only using classical physics to start, we'll get into quantum stuff in a bit)

What we think of as "dynamics" right now, the change of systems over time, is largely due to the rules about information being forbidden to flow 'backwards' in time for any observer.

Suppose, for example, we can describe a particle's position over time as x=vt. We observe the particle at t=0 at x=0, t=1 at x=v, t=2 at x=2t, and so on. Intuitively we think of this graph as 'realizing' over time (for lack of a better phrase); that until t=3, there's no meaning to the question "What is the particle's position at t=3?" We instead think "What will be the particle's position at t=3, assuming no outside forces intervene in the meantime?"

But it can be argued that the entirety of the particle's position v. time trajectory, its worldline is already entirely 'real.' The future positions of the particle are just as fixed as the past positions are. Ie, that all of time, past, present, and future, is one big, unchanging "block." (the very idea it could change is meaningless since time itself is contained within the block)

Time appears to flow, for us, because at x=2, t=2 some information carrying 'thing' (say a photon bouncing off the particle) happened that then interacts with us at some other position (say x=2, y=1, t=2+c*dt ). But our receipt of that information must always be later than the event itself because all real information carrying particles must travel at c or slower. The apparent flow of time is a byproduct of the laws of physics generated by the nature of time and how it is connected to space.

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So let's think a step forward from there. If space-time is one big block, for which the 'present' moment is just a slice of some hypervolume... then one can rather well think that a graph x vs. t is really very similar to y vs. x. A particle travelling under constant acceleration (while the speed is << c) can be well described as x = x0 + v0*t + 1/2at², a parabola. That parabola is 'just' as real as y = ax² + bx + c is in the y vs. x plot.

And, like y vs x can be plotted for complex values of x, y = ax² + bx + c , when x is a complex valued object, still has meaning. However, due to our limitations, physically, plotting y=ax² + bx + c is more difficult. We like, often to plot complex numbers using 2 axes, a real and imaginary. We'd need 4 axes in total to plot the real and imaginary parts of both x and y. One common approach is to make two plots, a plot of the real component of y for complex x, and the imaginary component of y for complex x. Each of these is a 3 axis "slice" of the 4 axes needed.

One other way to slice it would be to slice x into real and complex plots, and each plot containing both real and complex y components. And when you slice it this way, you'll see that the plot of purely real x only has a purely real y. It's the parabola we're already familiar with of the standard y vs x plot. The standard 2-d plotting y vs. x is, in fact, a reduced slice of the 4-d complex hypervolume.

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So going back to our universe... our space-time block may be one slice of a much larger thing. Here the nomenclature is tricky. I am going to specify axes as different from dimensions. Each dimension of space-time has at least the real axis. But one could well imagine that each space-time dimension has a real and imaginary component. Thus one would need 8 axes in all to describe this meta-object of complex space-time.

Our universe, as we know it, is one 4-axis slice of that space-time. And to buck tradition, I'm going to say it's the slice along purely real x, y, z, and imaginary t. Ie, in this meta object there is w,x,y,z, and our universe is the slice Im(w), x,y,z. Then the basic laws of physics (particularly those of relativity) start to fall out of choosing that particular slice.

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As to the beginning of time, let's look at our parabola y=x². If I ask you... what is x when y < 0... you say... there's no meaning to that question. Or, in light of the above discussion, you recall that our y vs. x graph is really just a subset of the 4-axis complex y vs. x hypervolume. Then you say that x can be some whole set of complex numbers, it just can't be purely real.

For whatever reason, Hawking and Hartle worked out a solution to our "universe's equation" that is parabolic as well. All of the real "stuff" in our universe is described with the constraint like the above parabola y=x². As you approach zero from positive t (heading in the negative t direction), you turn back around and venture forth once more into positive t territory. The only way you can explore "negative" t is to allow t to take on imaginary values (or, to use my above nomenclature, to take the real slice of w, rather than the imaginary slice).

But in this scenario, real w, {w,x,y,z} acts like any kind of standard 4-space. There's nothing we'd recognize as "dynamic" in it because it doesn't have any axis that "flows" like time does. At first this may be hard to picture, that a static universe becomes a dynamic one... but the notion of becoming is a byproduct of being stuck in the dynamic part of the universe to begin with. If space-time is, indeed, one big fixed block, then the subvolume we occupy is just as "static" as the 4-d subvolume where w is real. The difference is that the relationship between the worldlines of things we can call particles or objects obeys a different set of rules in our part than in the other part.