I'll give a rundown of how I build my frames. After building the first one, the second went together in about half the time.
Tools: Phillips screwdriver, drill and drill bits, angle grinder, 1/8" rivets, and riveter, marker, tape measure.
Materials: 3/4'' angle aluminum, Cutter Mau5 8 cob kit
After cutting my lengths and widths, I attach the heat sinks on the end of the frame first. Mock up how its going to lay and instead of measuring where to make the holes, I just tilt the heatsink up and mark with a sharpie.
I mark and drill out for each heatsink on the same side.
Quality craftmanship right here lol
After driling all the holes for the first side, I attach the heatsinks on that side. Next line up the other side and mark each heatsink, again I've found it to be easier and more precise to simply eyeball and mark for the heatsinks.
It comes together pretty quickly after you get in the swing.
After all the heat sinks are in place, square up your frame, drill, and rivet. One at a time is how I do, make sure your frame stays square and get after it.