I'd recommend leaving it to the pros if possible. Newer materials used by manufacturers may be more easily damaged than they would be on some of the older models of skates, and some models might not recommend baking of any sort. Many hockey shops will do it for free or minimal cost even if you didn't buy your skates from them. However, if you don't have access to a local hockey shop, you can do the following - at your own risk of course - which I have done successfully.
- Loosen your laces and place your skates on a baking sheet. I usually put a towel on the baking sheet first to avoid the boot having direct contact with the metal. Set the baking sheet with skates aside for now.
- Preheat the oven to 180 degrees. This would be a conventional gas or electric appliance - not convection, toaster, wood-fired or anything like that.
- Turn the oven off.
- Place the baking sheet with skates in the oven.
- Leave them in the oven for no more than 8 minutes.
- Remove them and begin lacing them up. Be firm but careful not to pull too much on the eyelets or you could rip them out.
- Sit with your feet in the skates for 15 minutes. Don't move around too much.
- Unlace your skates and let them sit for 24 hours.
You can do this one skate at a time or both at the same time. You can also repeat this at anytime to remold skates that haven't been used in a while or are going to be used on new feet. Again, try to let a hockey shop do this for you if can.