You could try putting them in a preheated oven at about 200 degrees (or "warm")

You put one in and wait about 5 minutes then put the other in. each one should not be in there longer than 10 minutes. You will also want to make sure that the liners are made to be heat fitted (moulded).

I just had a pair of telemark boots fitted and man what a difference over my Burton Ruler SI boot fitment.
here is what they did for me:

1.Take the footbet out of the liner
2. Take the liner out of the boot.
3. put the liners in the heat box or oven (lowest temperature) about 5 minutes apart (allows you to fit one while the other is still cooking).
4. take off your socks and get a pair of thin dress socks. This next part will require some thinking. You are going to make a "toe cap". this will make the boot pack down a bit more around your toes, allowing a more comfortable fit when you are riding. you can try to use another thin sock that you will wrap around your toes, or a cut up tshirt in the proper shape that will be ductaped to resemble a 1/8 inch thick cap that your toes will go in. it will go from the tip of your toes to just about the ball of the foot.
5. step on the footbed and then put the cap over the end of your foot (over the footbed) then put on the thin sock and pull it tight getting out all the wrinkles. Do this for both feet.
6. check on those liners! they should get pliable and warm.
7. Take the first one out and carefully slide your foot in with your toes pointing up towards your knee (not curled). put on the boot and stomp down 3 times hard. Quickly tighten the boot up nice and tight. your toes will feel snug in there because of the cap.
8. do the same for the other foot.

9. Stand in a snowboarding stance for about 10 minutes. this will set the flex. you could do this by strapping into your board and make like you are going down hill.
10. wak around for 10 minutes.
11. take off the boot and all the stuff in your sock. put the liners back in and get on a pair of riding socks.
12. put the boots back on and tighten them up proper like.

You are now fitted, at least that is how it was done for my customer tele boots

Bill
disclaimer: i am not a pro, but did see one do this to me with the proper liners.