I was actually thinking that, for a box as wide and deep as a Pi 4, the "4 window" solution would be ideal. Cut the panels, then cut four "windows" in each using either a jigsaw or you could cut four large round circles using a router and Jasper Jig or equivalent. (Adire suggests something similar to the latter for the internal bracing of their subs.)

• Adire Sealed Tempest Design (w/ multiple round holes in braces)