In expert mode, you need a lot of water in the late game to upgrade benches, make electrical components, and most importantly, make coffee.
In a regular world, this isn’t a big deal, you can place water on a block that has two one block deep gaps on either side of it and then immediately pick it up again to get two buckets of water. But this doesn’t work in expert mode! In expert mode, the block of water must be >90% full, or picking it up with a bucket will give you an empty bucket and remove the water.
However, there is a solution. Water which freezes to ice can be mined. When the ice is replaced, it doesn’t remember that it was formed from a partial block of water and will melt into a full block of water that can be picked up with a bucket. Thus, if we can create a way to split water into several small spaces, wait for it to freeze, and then mine those blocks, we can dupe water.
Here’s one way of doing it. This farm is located on a mountain near the South Pole. I can place a block of ice at the top in the middle of the kilns and it will melt and fall down the blocks into the sections below before re-freezing to ice. I always get at least 6 blocks, and usually get 8 blocks of ice for each ice block melted.
If you are in a hurry, you can place a block next to the water that hasn’t frozen yet and it will usually immediately freeze the rest of the water.