Well, I am a BE developer. We have FE guy and designer. As soon new projects kicks in, we all look at it and then we have 2 work-flows:
1) The design has been shipped with product specifications, which means that I can start working on some BE logic for which I don't need FE dev, and he/she can do her part of the job. When she is finish, all or part by part, I just pass BE logic in dummy-hardcoded FE data.
2) The design has not been shipped, and when all is done from designer, we proceed as in first work-flow. We don't start the project before the at least 80% of design has been approved. If some extra design changes are needed, they are handled in the process, and we must be always ready for that.