Warping is a function of moisture change not clamping. Clamps may affect the joints but they won’t warp the wood. That said, it is possible your job is not warped, it just looks warped.
If the laminated board just isn’t flat, that does not mean its warped. You could have over-torqued the clamps and “pulled” the edges up so that the joints were not true. a 1/32 error across 10 boards = 10/32 of rise (corner to corner).
A little trick that we always use is to do the clamp up on an old sheet of 3/4″ ply. “Just snug” the boards together, then clamp all 4 corners to the ply. Then cinch up the cross clamps to get the seams tight. We also use biscuits at the joints. To glue up multiple boards and get a good flat laminated board, your need to (not having any of these can cause your job to appear warped):
- edge the boards,
- alternate the grain (see illustration – Figure 1)
- have uniform moisture content in all boards,
- good glue coverage on the joints, and
- a nice tight (not too tight) clamp job.