The Upnalab repository includes a 3D printable frame. As an alternative I made a height adjustable aluminium T slot frame design similar to that which I saw in Upnalab videos and I guessed the sizes.
This is my parts list.
I hand cut a plywood board to support the top and bottom arrays. In retrospect my design can be improved. I would laser cut the support boards because they need high precision. I would use one size smaller T channel and reduce the cube size.
Perhaps the best frame design I’ve seen is the laser cut frame by dbeaven1.