I have started using Project Proposals in order to get students to spend more time planning their work. I ask them to provide an explanation and description of their proposed work, indicate materials they will need and any special techniques that they are thinking of using.
I sign off on the proposal, indicating what I think will work well, and asking them to clarify anything that needs more details. I also make suggestions about ways to extend or approach their project, and they are free to accept advice or go ahead as they want. It seems to be a good use of formative assessment and I get to have a say right at the start of the project.