Entrance Point Glitch (or EPG) is a glitch used to manipulate Link's last known entrance in the game, allowing him to respawn in a different location upon voiding out. Link's entrance from doors that open and close in a sliding animation is set when the door is closed. By standing at the farthest point that you can open a door, placing a bomb, and opening the door on the right frame after the bomb explodes, you can delay the closing of the door, but still walk to the other side. You can get in the right spot for the trick as Adult by standing at the left corner of the door and crouchstabbing left.
After walking far enough away from the door, the door will close, and Link will take damage from the bomb. If you place Farore's Wind, or void out, you will be put at the place you stood when the door closed. If you stand next to a wall (and face it) when the door closes, you can void out and respawn inside or through the wall. This is useful for getting out of bounds or accessing unloaded rooms.
For Child, the frame you need to open the door is the first frame the bomb explodes, and is 2 frames before the bomb explosion hits Link. It looks like this:
For Adult, it's a little bit different. You'll want to use the frame after the Child frame, which is the second frame of the bomb explosion, and the frame before the bomb hits Link. It looks like this: