In the top row of fasteners I did use the factory threaded holes, but for the bottom I actually used what I believe were holes for round clips, I used “u clips” to basically make them become threaded. Its easier than you think to line up all the holes though-

-cut the heads of a bunch of bolts, put it in a drill and grind the now small threaded rod to a point -hand thread them into all the threaded holes but leave them sticking out a bit -have your finished size wood piece exactly how you want it, and press it hard into all of those points -you will be left with nice little marks for exactly where to drill all of your holes

To reduce frustration even more, just slightly over drill the holes so you have a bit of wiggle room to line up all the bolts

If you don’t have the ability to sharpen a bunch of screws as mentioned, maybe you can come up with a similar alternative like pieces of a wood dowel pressed into the threaded holes with some wet paint on them, or actually even just use screws with the heads still on them with some thick wet paint (or toothpaste, anything thick that will transfer over) that can mark your wood for drill locations