DISCLAIMER: I don’t know if this is the only route to beat the “puzzle” that it is the final maze for Sword of the Tall. I do wanna note that sometimes (not sure) which entrance you are getting is random. The one in the video sometimes popped us as the third, sometimes as the second and sometimes as the fourth (Yes, I tried this several times till i figured it out, also got 15 levels out of it.)
In order to get an entrance you press the mechanical tile/cube and you’ll go down, eventually you’ll reach a floor with a dozen Flans and a Giant. in the centar of that room there’s another mechanical tile/cub. Press it up and you’ll go up to the place where you first went down. Note that there’s a red button; This one takes you to the entrance of the dungeon. You’ll probably get a second tile/cube, go down and you’ll face another dozen flans and two giants (it maxes out at three giants and a medusa).
If you are lucky the third time will place you at the start of the video. If you are wondering what’s waiting for you after the video, it’s a level 38 boss that its easy compared to the Giants.
EDIT: Dunno why the PS4 recorded with this quality, but it is what it is!