Two piece templates are much easier to use. For the wing you are going to cut as I said before forget the pivot method make two, two piece templates.

This assumes you are adding a balsa LE.

Make clean vertical cuts on your foam slab so you have a slab that is the correct size with tip and root angles set correctly. Align the templates so you have the flat of the back of the LE on the front edge of the slab.

Work from the front to the rear. I like to have colour coded points on the templates because I work on my own but numbers work too, esp. if you have a helper.

Cut the top first remove the top part of the template and cut the bottom front to rear. The stub on the front of the LE on the template makes sure you get a clean entry on the foam.

There is a good chance of ripples on your first attempts. They are caused by hesitations on the cut [ or bumps on the templates. ] Sand them fill with light weight spackle and they are good to go.

Most people I have shown how to cut get pretty good results after 3 to 4 attempts.

Wipe the stringy bits of the wire after every cut. Do not be tempted to go for a 'really hot' wire, one I found it much better with just hot enough to cut slowly is easier to manage.

HAVE SOME POSITIVE VENTILATION GOING AN EXTRACTOR FAN IS GOOD BUT OPEN WINDOWS AND ANY FAN BLOWING AWAY FROM THE WORK TOP IS OK.

Pic is not mine but I used something similar. JD