I built mine out of shower white board and 2x4s. Mine is just wide enough to hold the ½" conduit that I use to hang stuff on. The bottom can have a tarp --or for me, the powder just falls straight downward and I/we use a vacuum cleaner to pick it up after finishing all the powder painting.
On one of the 2x2" wood ledges that hold the conduits, I placed an aluminum angle piece that runs from the front to the back in which the ground wire is continuously clipped to. When the pieces on the conduit are moved to the stand (after pre-heating them) I do not need to worry with connecting the ground wire.