Wwhat is heat molding your boots?

It's custom molding the liner to your foot using heat to warm up the liner and then putting your foot into it and it mold around your foot. Only certain liners can do it though, and only certain boot warmers can reach the temperature required to mold. Go to a bootfitter or shop and see if you can mold your liners or buy liners for your boots that can be molded, it's extremely worth it - it makes ski boots SO much more comfortable.

^ this.  and when you try them on, they should feel a bit hard, especially around the ankles.  Just make sure you get the footsole right, with a rubber insert for the toes to give you a little more room.  Takes about .5 hour total, but so worth it for comfort.  I have the il moros with ID liners and they be the shiat