Some questions you can ask yourself at the beginning of the course:
When you start thinking of a course, you might be thinking of a very broad topic, which would easily fill several modules.
If your idea is defined, it is possible that it could still be divided into several parts.
For example, if you are going to create a module on baking: you want to share your expertise of baking a chocolate cake with chocolate filling and decorated with a woodland scene. Could this be divided into a module on baking the cake and a module on decorating the cake?
Do your students need some previous knowledge or skills before starting your module?
For example, do they need to know how to use a food processor/an oven?
What tools, if any, are needed to take your module?
For example, to bake a cake they will need flour, an oven, a mixing bowl etc.
Make a list of the skills/knowledge your students will have gained after taking your course. Start with the broadest concept, and drill down to smaller individual skills/knowledge.
For example, at the end of my module, students will know how to bake.
More detailed: they will understand how to measure all the ingredients. They will understand in which order the ingredients must be mixed. They will have a good idea of what a cake filling is and how to make one.
List all the steps necessary to reach the desired outcome (add as many steps as required). Re-order the steps if necessary. It is sometimes easier to start with the outcome, and ask yourself the question: to reach this result, what do I need to do first?
Would this step be better served by video, text, photo, or a mixture of some of those?
For each step, think of practical exercises you could ask your students to do, and some questions to test their new knowledge and skills.