×Interesting how the switcher sometimes disappears into the water, and sometimes does not.

×The easy part is getting something to the northeast plate. That can be done dropping four trapdoors, which leaves one for the cleanup. That's the hard part.

The key is to chase queens and roaches out of troublesome parts of the room earlier, so you have as little as possible to deal with before the last swap. The hardest part to deal with is the southwest area, so focus on clearing that out as much as possible. It also helps to avoid having more than two roaches in the southeast area.

If you need more help, here's an image showing which trapdoors I used for my first four swaps and where the roaches were at the time:

×clear out roaches immediately if you can. There's no time pressure at all, so you can afford to wait several spawn cycles of that helps you to clean up the roaches.

× Queens are bad. You really want to get rid of them as soon as you don't need them anymore.

× Also: you will probably end up having a couple of roaches running around in the end. Just make sure they are in locations where you can burn them by turning them into queens, directly or using specific timing.

×Wait for a stack of three roaches in the first niche, just W of the hot tile, then move right.

×You now have one roach in the second niche at the bottom. Step on a swap token to make it go N and E. Three queen at the W will automatically die on the first hot tile.

×Make sure to swap at the right time: the queen going N and E should spawn a couple of roaches before she hits the hot tile. Meanwhile, move right to capture the newly-spawned roaches at a convenient spot further on.