Old Windmill
I completely rebuilt my old windmill to fix some details that no longer suited me. The new version uses about 10% fewer blocks and is more detailed.
I made three variations in limestone, sandstone, and black shale, with exactly the same shape, and others are easily doable in creative mode.
It was built on the grid, if you want to keep that, change the blueprint's pivot to "Selection Area (Legacy)" point in your settings (Miscellaneous -> Blueprints).
There are a few blocks around the mill to make it easier to place back on the grid; you'll need to remove them. It's also designed to be sunk into the ground down to the door level; feel free to add a few steps at the entrance.