Gluing the foam to the wood for sanding is not critical. Whatever it takes, hot glue, epoxy, etc., to hold the foam in place for sanding. The critical part is the bonding of the glass cloth to the spars or other wood structure. Make sure the wood is clean and free of dust to insure the best penetration of the pure epoxy bonding the glass to the wood. The process may seem like rocket science but it's not.
Larry Flesner
