Do you use 3/4" pipe clamps???
Get a 24x48 piece of Melamine board, about $11.
And a 48"x2"x4" or 2x6
I found a piece of 2x6 in the cull lumber bin for $1.
Stud lumber has the edges relieved so cut off a smidge on the table saw to square them up. No table saw? Doesn't matter.
I ripped the 2x6 to 2x5. Then drew a line right down the center with cross marks every 6".
Now you drill a 1" hole at each of the marks. Use a 'Speedbore' or other brand Spade Bit. If your pipe clamps are 1/2" drill 3/4" holes.
Rip the board right down the center. Check to make sure the holes line up! Then glue (polyurethane 'cause of the melamine) and screw the pieces to the edges of the melamine. Put some Linseed oil or shellac or whatever on the wood so glue cleans off more easily. Tite-Bond, etc., won't stick to the melamine.
You're clamps won't creep or fall over ever again. And the "B" side is an always clean, flat work surface.
If you use bar clamps, rip the two pieces w/o drilling holes, clamp them together and cut Dadoes the width of your bars.
Sorry 'bout the foto; too lazy to get out the floods.