for this you need a level 2 body crystal and a level 2 fire crystal. this is so you can get the flaming fist skill, which lets you make a fist with fire magic equipped for a super-powered punch that also gives you a boost in midair. You need the body crystal for the flying kick skill, which give you a boost when you kick in midair

Now all you need to do is equip fire magic, jump in the air, then kick forward and fire punch at the same time. the boosts from each skill stack and you go flying at like mach 3 across the level. I like to do the kick and then the fist after because the flaming fist skill negates fall damage

BTW doing both of these will almost guarantee a kill if you happen to barrel into an enemy with both boosts at once (no armor can protect from the human cannonball)