Am considering these type of frameless clip frames:
https://www.frames.co.uk/ready-made-frame/15/clip-frame
18cm x 24cm
And then fix each frame into place using L pins.
If I present 12 grid drawings – 4 x 3 – then using these frames, placed alongside each other, will take a minimum wall space of:
width: 4 x 18cm =72 cm
height: 3 x 24cm =72 cm