Specify the core principle of the design
When you are designing something new, there is a core idea behind how the design works (whether you know it or not!) This core idea is called a design argument. To better to design, test and communicate your design you need to articulate your design argument.
Fortunately, there's a really straightforward way to write design arguments.
Plomp (2007 ch.1 ) gives a few examples of a design question that can serve as a research question:
What are the characteristics of an effective in-service programme for mathematics teachers through which they develop the ability to apply student-centered pedagogical methods?
What are the characteristics of an in-service arrangement that facilitates the implementation of MBL5-supported lesson activities in physics education (Tecle, 2003)?
And here is an example of a design argument from Easterday, Rees Lewis & Gerber (2016):
If you want to design a <computer-supported help-seeking> intervention for the purpose <of increasing industrial design abilities> in the context <of an informal, extracurricular, university design clubs>, then you are best advised to give that intervention the characteristics <access to professional mentors that can provide feedback, direct instruction of help-seeking strategies, establishing routines to surface problems and online tools to track help requests> (substantive emphasis), and to do that via procedures <selecting mentors with expertise on students’ projects> (procedural emphasis), because of arguments <from principles of help seeking and feedback from learning sciences, surfacing problems from organizational sciences, and designing online communities from human-computer interaction>.
Note that in addition to the design argument itself, you would also have to justify the different parts of the argument based on references to the literature.
van den Akker (1999) developed a very concise format for design problems and design solutions. Note that when framed in a general way, the design question can serve as your research question and the design solution (i.e., design argument) can serve as a hypothesis.
A design question can be written as:
What are the characteristics of an <intervention X> for the purpose/outcome Y (Y1, Y2, ..., Yn) in context Z?
the following form for design arguments:
If you want to design intervention X for the purpose/function Y in context Z, then you are best advised to give that intervention the characteristics A, B, and C [substantive emphasis], and to do that via procedures K, L, and M [procedural emphasis], because of arguments P, Q, and R.
Notice that the design argument has several parts:
1. What is the difference between the substantive and procedural emphasis.
Let's say you are making a design intervention to teach art to middle schoolers in public school and you want it to be motivating. Now you could specify that the design intervention will involve art projects about cats -- that will motivate the youth! That would be a substantive emphasis in the design argument.
Except, in this case, you know that substantive emphasis won't work for all the kids. So rather than specify that the teacher make the intervention about cats, you could specify that teachers survey kids before the intervention to find out what topic will be most motivating to the majority of students. In that case, you are saying that the designer/implementer should carry out some process, i.e., a procedural emphasis rather than a substantive emphasis.
You may have a design argument that only consists of substantive elements, but it almost surely will involve procedural elements if you expect it to work in multiple contexts.
Easterday, M. W., Rees Lewis, D. G., & Gerber, M. (2016). The logic of the theoretical and practical products of design research. Australasian Journal of Educational Technology, 32(4), 125-144
Plomp, T. & Nieveen, N. (Eds.) (2007). An introduction to educational design research. Enschede: Netherlands institute for curriculum development.