Recording, brainstorming, connecting, analyzing, researching, collaborating, revising, planning, designing, sketching, and quoting. Effective writing skills are an essential piece of multidisciplinary projects--the piece that is most often left out--but arguably the most important to facilitate depth of learning as well as transfer of learning. Check out this blog series about using Thoughtbooks across disciplines or this resource about creating a culture of writing.
The power in STEM is not in the subjects but the interdisciplinary learning, which helps students see relevance, develop deeper learning, and facilitate application of that learning. In other words, it doesn't just have to be STEM or even STEAM subjects. For example, if students are solving a business problem, they might learn finance, marketing, art, management, technology, etc. Finding common ground through the business problem ties all of the subjects together in purpose, but using the right forms, methods, and knowledge is what leads to success. Learn more about interdisciplinary structure in this blog post here.
In order to help students find, connect, and deepen their learning between disciplines, there must be a facilitator (usually the lead teacher in the interdisciplinary focus) who builds time in the schedule to coach students and guide them in how to make sense of the vast array of knowledge across disciplines. This is a crucial role and should not be taken lightly. At an elementary level, this would obviously be the teacher, but there is always flexibility. At the secondary level I have seen outside facilitators that come in specifically for this task, home-room teachers, the primary subject teacher for the project, or even the English teacher who frames the thinking, reading, and writing around the purpose and focus of the project (my personal bias). More resources on facilitating coming soon.