It can take anywhere from a day to a week IME. Some pieces might be a bit more pesky. Depends on the pieces, but I suggest folks soak them for a good week prior to use, then a stone to hold them down. After a week's worth of soaking, they are much easier to place and keep in the spot you want.
If you have a specific angle you are after, then drilling or cutting some wood, or the extras, can help "shim" the piece/s to the correct angle, pre drill the holes and then use some screws or nails etc.
You can also screw slate or other flat rock on to the wood in other postions, then remove later. Straps and ties have not been particularly good IME.
Soak first though, then add.
I like the burl base trimmings which take the longest to fully sink, I soak them a longer time, but many just slate them. Either way.