Yep, do it with my intuition linings both water and snow.   Use a convection oven and temp of about 225.  Makes sure your oven doesn't run hot.   Put the liners on a cookie sheet.  Warm them for about 5 minutes and then flip them over for another few minutes.  They should come out expanded and puffy.   You do not want to over cook them as it will ruin them.    Make sure you make a toe cap so you have a little wiggle room.  I just stuff part of a paper towell in the end and then jam my foot in there.   Put your liner in the boot, put your foot in the liner and then stand in them similar to your ski pose until they cool down.   They are a bit warm so you may want a thin sock on your foot.   If you need more detail let me know but it's rather easy.

the attached link has a video on how to heat mold.

http://www.jagersport.com/vidproduct.htm