Included are three different designs, which have either 1 centric, 2 horizontal or 2 vertical nut holes. The four legs are inserted into the shelf holes. The fitting is just right when I printed mine, but I included the FreeCAD file for anyone needing it.

I printed with 0.15 layer height and 15% infill with PETG.

I am working on using my Ivar for indoor growing. Not planning on hydroponic-system, but might look into it in the future. Currently I just put LED-strips on the bottom of the shelf and grow in containers underneath.