Unstick Button can also be used to get under the map right as the game begins

[herr.sauber1]

When you use the "Unstick Hero" button you get pushed under the ground when in the countdown map but if you spam jump after you pressed the "Unstick Hero" button you will spawn under the normal map and you can fly around a bit before you fall and get teleported back up. Seems to only work when you get pushed under that block at second 5 in the video, if you don't press "Unstick Hero" early enough the game will spawn/push you above the map before you have time to react.
View attachment unstick_bug.mp4