I didn't drop many trapdoors on this one.
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×I went in along the edge, and opened the bottom crumbly wall so he'd have to come out around a diagonal.
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×Then there was some zig-zagging to create a whole bunch of them (I had way more than three), as I worked my way between the plates and out.
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×Also, remember that it's good enough to get them hung up on the force arrows as you make your way out. You can center them from outside where there are no trapdoors.