If you are determined to start learning vacuum bagging -- read up on relative pressures and how to read them
also pressures allowable for white 1 lb foam - about 2 PSI (not water or mercury -)air is about right - there is lots to learn - keep edges all close to foam -no overhang -it will smash -
also if the foam blocks are not right - your product will be warped ,bowed or twisted - but if you read up you can do the first one OK
Frankly, the clamp is far easier -if you have a clamp---
Once you get by the first go around the next few hundred will go easier ---