Hi everyone! I have an 18" square x 5/8" piece of particle board that I need to stand a 6' by 1/4" or 1/2" rod on it that is detachable. It does not have to support much weight, just a few ounces(it's for a balloon tower). I'm looking for an economical solution, but I prefer not to use PVC pipe as it's walls are too thick and the diameter ends up being too large. Any ideas of what parts/materials I should use to do this?

if I understand that you need the rod to stand up on a board that is laid flat on the ground as a base, you could cut a piece of 2x4 into a 3-1/2 square, glue it to the baseboard, drill a hole through both, and use a piece of 1/4 or 3/16 PVC pipe as the rod. just drop it into the hole, and the job is done.

a solid iron rod poses a larger chance of injury if somebody should trip and fall on it.

I would get 1/4/20 threaded rod (all-thread) and a 1/4/20 T nut. You need a bit more thickness on the base, so a double layer would be better. Mount the T-nut on the bottom and screw the all tread in.