Stand facing the door in the previous room, at a specific distance from the door, approximately a 3-pixel window at an effective distance of a 6-tile closed-end runway (taking into account how slopes can modify the effective distance). Pause, then unpause while holding dash and right. If positioned correctly, the unpause fade-in will finish on the exact frame that the transition would occur, delaying the transition by a frame. Samus will spawn standing inside the Power Bomb blocks and be able to X-Ray climb.