gotta say that looks pretty good !

to locate the board ....

you have to have references cut into the foam block from the top side ... this is because the block is not accurate enough to flip over and carry on cutting

so instead of cutting the whole of the top of the block, id cut 6-8-10 (as many as you need to support the foam block) square patches into the block ... then when you flip the foam block over these machined patches locate onto the table by mean of MDF pieces that are the same size as the patch that was cut

hope it sorta makes sense :D

what software you designing the board in ?