The Eck Skip is done on the boss level, where repeatedly doing a super jumps on the boss can boost you to his 2nd platform, where you can hit him again, making you skip the 2nd phase of the boss fight. TheCeddyWithin said it is possible to hit the boss during the skip, killing it instantly, but I have yet to replicate it. For the technique, I like to turn the boss slightly right, jumping somewhere between the forehead and nose bridge and tap backwards while I boost off the boss.