I have several sets of foam stab cores that were CNC cut years ago from 1/2 lbs density foam I had sourced. I sent the foam to the cutter and he proceeded to cut incredible cores....extremely accurate with a fully radiused LE. The core itself weighs only 11 grams, however, the ribs (10 ribs on each stab half) weigh less.
Molding the LE around the foam was straight forward...just spritzed 1/16" sheet with Windex and formed it around the LE with tape. Then held it there with the husks until dry. The LE's are as accurate as the foam core is. The final fitting is done on the stab half.
Bob does his differently: he cuts a block of foam into the shape he wants using only LE templates. He releaves the mold of the sheeting thickness. He wets the balsa and inserts it into the female cavity, following it up with the male piece. Then he squeezes the mold together pushing the male piece into the female and lets it dry. The point is that there are a few ways to mold a wing or stab LE. The two I discussed are a good start.