This is a simple block that allows you to arrange your parallel clamps perpendicular to each other for clamping rectangular objects. You can also just use the upper sections as spacers to get your clamps elevated enough to fit cauls during panel glue-ups.

Should print without supports. I set the dimensions for Bessey K Body parallel clamps, but with a pair of calipers you can easily adapt them to any sized clamps by adjusting the dimensions in the spreadsheet in the FreeCAD file