yeah. i used some toes from socks. i would definitley use a couple extra to make a exagerated toe box.
but to the OP it sounds like youre a little young and shouldnt be using the oven for brownie, let alone baking liners.
but if you do, 200 degrees, pop the liners in when its pre heated, close the door and shut the oven off. take em out after 10 minutes.
while you do that, put you foot bed and "toe box" in a mid weight sock.
stick the liner in the shell and pull up on the back, and make sure the liner is fully overlapped.
buckle to medium, slam your heels on the ground, and put your toes up. keep your knee bent, and let cool for 15 minutes. have a beer, this can be painful.
then take em off, let em cool a bit longer, and put them on using a normal ski sock (no extras in it)
if theyre tight, theyll loosen up after a couple days of shredding.
ive done it three times with my boots, and fucked it up everytime. its pretty hard. ive heard that stretching the shell open helps a bunch.