Obtain a Flash Suit from the Business Center elevator. Uses: shinespark to bypass gates to get Ice Beam in Dashless categories, or obtain a Blue Suit without needing Speed Booster. After reading this guide, click here for setups using different elevators.

Setting up

First, make sure you meet all the criteria for crystal flashing: Empty any Reserve Tanks, Energy is 50 or less, have at least 10 Missiles, 10 Super Missiles, and 11 Power Bombs. (Since the Power Bomb placement is tricky, the more you start with, the better!)

Second, turn off ALL BEAM upgrades.

Now, stand on the elevator, slightly off-center, and face left. Note the 4 horizontal lines in the background above the elevator.

Here's what you do

Jump and do a mid-air morph while ascending. (You should be in ball form when you hit the ceiling.)

On the way down, lay a Power Bomb so that it's in the center between the bottom two horizontal lines.

As soon as you lay the power bomb, unmorph and hold R+Shot. (You don't need to worry about standing, since the bounce from the bomb will stand you up.)

Count 5 shots, and as soon as the fifth shot releases, press and hold L in addition to R and Shot. (I actually count it off like 1-2, 1, 2, 3)

Press down as soon as the 5th shot hits the ceiling. Here's the key: The correct frame is when you hear the collision sound effect, but before you see the explosion.

Why does this work?

Bonking on the ceiling will normalize your fall speed and ensure that you pass through the correct vertical pixel.

When you lay a Power Bomb, your beam is disabled for a moment until the PB enters the second state of its animation cycle (it starts spinning faster after a moment). So, by holding Shot, you will fire as soon as your beam is unlocked, therefore the timing is consistent!