Flux Construct

At the start of the fight the core is usually buried in the stack. Wait until it forms a shape that leaves the glowing block on the outside, then shoot it. A Keese eyeball helps when the block is moving. Ultrahand can grab the core if it is loose and yank it away from the body. While the core is out, hit it with anything. When its health runs out, the rest of the blocks collapse.

When it flattens into a platform, get underneath and try Ascend if the slab is thin enough. You come out next to the core instead of climbing the side while it rearranges. Recall on a block it just threw can send that block back into the body and open the core. There are three ranks. The higher ones have more health in the same core, not a second weak point.

The core is the monster part you came for. It is a strong fuse and an upgrade material. The plain blocks do not fill your inventory with anything useful, so do not spend the fight mining them. Sky islands are the reliable spawns. A Blood Moon rebuilds the same construct on the same island.

Soldier constructs on the same islands are a different enemy. They have a body and a horn, and you fight them like a camp monster. A Flux Construct ignores that approach. If your weapon bounces, you are hitting a block. Look for the glow, even if it means waiting through one more transformation.