Polyiso is commonly available in compressive strengths of 16-25 psi , adequate for roofs where foot traffic is limited to installation and maintenance, not for an occupied basement.

Instead, use XPS, which comes in normal strengths of 40-100 psi.. But it must be followed by one or two layers of ply.

If you want to forego the insulation, use a bubble membrane product, such as Delta FL.

Before applying laminate, be sure the manufacturer warrants it for basement use and use the subfloor materials recommended.

Polyiso under the slab is isn't very effective either.