In reply to Nemo9:
I've done it a few times. I loosely followed the advice in the link posted above.
Best advice I can give is to clean the oven first and keep checking every 60 seconds so that you see the liners soften as they get to the right temperature.
On my feet I wore ski socks, with two toe caps made from the toes of old wool socks. I pulled a pair of womens knee high tights over the top of the socks to hold them in place.
One of the times I lifted my toes up by standing on a couple of books, this certainly didn't make things worse, and may have helped the heel pockets to form.
Final tip, do one boot at a time, less to worry about.
My girlfriend was a bit shocked when she looked in my oven and noticed that I'd cleaned it.
Post edited at 20:55