To access Sakon's Hideout at any time, go to its entrance on the first or second day. Put on the Bunny Hood. Hold Z and roll directly at the right crack of the hideout's entrance. If you aim and time it properly, you should roll through the wall and jump behind it. Usually, you'll end up in Sakon's Hideout; if you miss the jump, however, then you'll fall into some water outside the map, die, and respawn at the entrance to Ikana Canyon.
Once inside, you can explore the hideout freely. Kafei will not be present, and his introduction cutscene will not play. Morph into Goron Link and stand on the first switch. Quickly roll into the next room before the door closes. (If it closes on you, you will die and respawn outside of the hideout.) Kafei will then appear in a cutscene (and vanish afterward), and you will warp back to the door-opening switch. You can then kill the Deku Baba. Do so, and return to the other side by rolling to it from the switch. The room with several switches is the farthest you can go[verification needed], though you can kill one of the Deku Babas past the next door using your sword.
Interestingly, when you enter Sakon's Hideout early, the conveyor belt moves, but the mask on top of it does not. If you equip a transformation mask while in the hideout, the camera angle will glitch, revealing a purple-colored infinite void outside of the map.