Design method is like making a plan for building something really cool, like a spaceship or a castle. First, you need to think about what you want your spaceship or castle to look like and what it needs to do. Then you need to draw lots of pictures and make models to help you figure out how it will all fit together.
Next, you need to think about all the parts and materials you will need, and how to put them together in the right way. You might have to do some math or science to make sure everything works properly and is safe.
Once you have a good plan and all the materials you need, you can start building your project. But you still need to be careful and keep checking your plan to make sure you are doing everything right. And if something doesn't work out, you might need to go back and change your plan to fix it.
In the end, your design method helps you make something really awesome that you can be proud of!