Insert acrylic spacers in all extrusion channels facing the outside of the frame. Each extrusion has two outer facing channels.

In the layout shown in the second image, insert the acrylic spacer inserts and M3 nuts in all 8 of the outer facing channels. There should be (2) 5mm spacers, (3) 81mm spacers, and (4) M3 nuts in each channel.

Insert (2) M3 nuts in each of the remaining 8 channels.