I don't have room in my garage shop for a permanent clamp table, so I made this folding version from a leftover 2-ft.-wide sheet of 3/4-in.-thick plywood. Folded, it's less than 2 in. thick, so it stores neatly in a narrow space. First, I crosscut the sheet to 60 in. in length. Then I made a rip cut to create the 16-in.-wide base.Next, I drilled 1-1/8-in.-dia. holes at 4-in. intervals down the middle of the remaining 8-in.-wide piece. Ripping this piece down the middle created two racks with half-round cradles for pipe clamps.
I attached these racks to the base with screen hinges, which are flat on the outside, so they can be surface-mounted (I bought four 3-in. screen hinges for less than $4 at my local home center). I mounted the hinges on the inside of the racks, so the racks sit on the base when they're open. Friction-fit spreaders lock the racks in position during use. I made the spreaders 3 in. wide so they sit below the half–round clamp cradles. When the table folds for storage, wing nuts hold the spreaders on the base.