I am sure there are many ways of getting this done but I managed to get it very quickly once I tried to divide the bridges + trapdoors into sections that can be solved on their own without taking that much time.

×One way to divide the island in particular is imagining a line that goes through the power token and diagonally to the NE through two checkpoints in the water.

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×It's possible to clear the entire half the construct starts on first and only then move it to the other one and be fast enough to get the challenge.

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×Turn 48 was when the construct first stepped on a trapdoor on the other side and there was still enough time to get rid of the remaining trapdoors.