For this trick you must have the swordless link trick. First get on Epona and go to lake Hylia, go to where the 4 pillars are and position Epona so she is facing in the direction of the frozen entrance to Zoras domain. Equip the iron boots and play an ocarina song so that you aren't on Epona slowly walk forward so that you don't cause Epona to nay and walk backwards. Keep going until you fall in front of the entrance, now push the A button, but right after you do that pause and switch to the Kokiri boots before you actually mount Epona. You will now be sitting in the water but re-equip your iron boots so you have enough depth to switch boots back and swim toward the entrance to Zora's Domain. If you did it right you should warp to Zora's Domain, once there quickly equip your iron boots so as not to rise to the surface or you will be pulled on top of the ice.