First I print out the airfoil using Profili, and stick it to some 1/8 balsa with spray adhesive (photo 1). I cut it out as in the second picture and discard the bit from above the airfoil. Then I glue some 1/64 ply onto the top of each of the two remaining pieces. The hotwire will run smoothly on this. You could possibly replace the ply with thin flexible wire if you can't get the ply.
I leave extra ply at the ends of the templates as shown on picture 3.
I cut the foam block to the shape shown in the plan. I do it by drawing the lines on the block, then weighing it down on the bench with the offcut area over the edge. I sit my cutting bow on the line and turn the power on. Gravity pulls the bow through the block. Repeat for all four sides of the wing blank and you have a foam block in the planform of the wing half.