× Actually there is a strategy I used here and I think it's not all trial and error, you need lots of golem + mirror manipulation to complete this. As you already noticed you can't kill golems on the pressure plate so you must kill them on the normal tile and on the shallow water.

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This is the order I used to kill the first 5 golems, I started from NE. To do so I used the mirrors and I never crashed them, that's something you can do after you kill the Sixth golem.

×I can kill three golems from the lower-left giant and get the last stuck in the shallow water, but I can't kill the last golem without exposing myself to the lower-right giant, and whenever I try to kill that giant, a golem steps onto the pressure plate and I can't find any way to get it off again because all the spots that might work are already occupied by rock piles.

×Mirrors at (19,18) and (21,16) can keep the southeast giant in place while you take care of the golems from the other two giants.

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Holds:
Nanfro Budkin's First Dungeon,
The Puzzle Catacombs
Graphical Mods:
Power Station (AE)

×That was actually easier than I thought it would be, because the whole time I had been thinking the pressure plate was a toggle. That's what I get for not checking!