having this table will make it possible for you to stack your Ultimaker on top or on bottom of another ultimaker just like the spacer does, but your advantage with this one is that you can use it as a table too.
Technical
I advice you to use
6 mm ply wood to make it perfectly fit and in the same style as the ultimaker.
12 * 16mm M3 bolts, socket cap
12 x M3 nuts, Hexagonal
2mm Hex-screwdriver