This is what I have done.
Drill many one inch holes in an eighteen inch long piece of 3in. plastic pipe. Fasten the pipe standing up vertically to a piece of plywood with a screw from the bottom into a piece of wood wedged into the bottom end of the pipe. Make a conical shape from a large black plastic pot.
Around the pipe standing up on the board make the base of the pedestal about ten in. dia by about three in. thick. Then set the black plastic cone on the base concentric with the pipe. Fill with mix from the top end of the cone while tamping it down and into the holes in the pipe as best you can. You could also put a cylinder of chicken wire around the pipe for added strength. I also use reinforcing fibers.
If you leave about an inch of the pipe stick above the cement at the top of the pedestal, it can be used to center and locate the bowl.
After the piece cures for several days, slide the plywood to the edge of your table and remove the screw holding the pipe to the plywood.