What about the beginning? To create a student-selected project, the teacher has to have a skill set in mind for students. We know that we learn best when we teach others, so I often lean toward that kind of project: creating products for others' consumption. I've had students make narrated slideshows and videos to reflect their own understanding of topics, and then shared those links with others, for example. Here's one on homesteading in Montana.
We learned a lot about the Montana Gold Rush first. We did some reading with primary and secondary sources, and we took a field trip to Helena to learn with Montana historian Ellen Baumler. Each student did mini-research projects and shared their learning with the class. Then I gave students the project's parameters and based on this, they selected their groups and their topics.
Student writes hashtag for primary source photo on hydraulic mining
Every day they have to check in on our google classroom - what did you accomplish today, and what is your goal for tomorrow. Each morning I read their goal back to them. A couple of days ago we made a to-do list on the board as the countdown to dress rehearsal day neared.
Today is the dress rehearsal, and we are on a tight timeline for practicing each others' activities. The fourth graders will be here after only one more class!