I made this like a few months ago. Although, I think I made the inner frame in a couple of days after I finished the prototype.

Some of the holes aren't flush since I had to re-drill the second pla plate. Normally I would drill on both pla plates first then reshape the pla plates which should make the holes align perfectly. However, since I will cement the runers inside the inner frames that kind of precision isn't necessary for this mod.

As for the holes, I always mark the center first before drilling it. The mark should at least help your drill bit get a grip on that first touch. Then I just keep my hands perpendicular with the surface.

If the holes you're making are long/deep, you might wanna stop now and then to check if they are straight.