Overworld:

Upon spawning in, make your way to the waterfall. It will be at the opposite side of the map. Get to the left side of the waterfall and locate an invisible truss, jump onto it and climb to the top of the waterfall. Get to the far right corner of the waterfall, there should be a truss there. Climb it until you get teleported into a space area.

Space:

Using third-person view, look outside of the space-box for a structure that looks like it shouldn't be there. When you find it, walk through the wall into the center of it, look back where you came from, and without jumping, walk forward. You should drop down into a maze.

Maze:

When you drop in there, take the far right path. At the first 3-way intersection, take a left. Take another left next chance you get. Go through the tight gate to the right at the next intersection, and cross at the one directly after it. Once you reach another intersection, take a right, and take a left immediately after. After the zig-zag part, take a left. When you reach the dead end, look up, there should be a transparent platform above you. Jump onto it. Now go straight ahead, and drop down again on the opposite side of that platform. Once you reach the dead end of this part, jump up into the hole that should be to your left (it's high up, so this may take a few tries) Simply go forward, and you'll see Undertale Doge in front of you.

Happy new years by the way, and enjoy destroying my records.