What are those conditions, in a nutshell? I would highlight the following:
Thought-provoking intellectual challenges (inquiries, questions, problems)
The challenge has been designed to optimize self-sustaining and productive work by learners, related to a clear and intellectually worthy goal
The learners have become reasonably competent in classroom routines that foster productive goal-focused work
The challenge cannot be accomplished by a worksheet, checklist or recipe. It requires strategic use of knowledge and skill, creative problem-solving, and critical thinking; and the eliciting of multiple perspectives on how to address the challenge and gauge progress.
There is an unambiguous product or performance goal (even if there is ambiguity about how to achieve the goal), supported by clear criteria and standards, thus permitting ongoing student self-assessment and self-adjustment.
There is enough feedback within the challenge (and resources) that the work can be maximally self-sustaining and productive.
The teacher is therefore freed up to coach for a significant amount of time, permitting personalized feedback and guidance (as well as just-in-time mini-lessons). This coaching role also permits the teacher to determine what is and isn’t working in the challenge, and thus enables the teacher to quickly change gears if the desired learning is not occurring or the process is not working.