If you are familiar with Khan Academy then you know how nicely he sets up his videos. The great news is that it is actually not too hard to do yourself.
https://www.youtube.com/watch?v=1tjJDdszcZg&feature=youtu.be
If you are fortunate enough to have been supplied a document camera by your school, check out this link to learn how to set that up https://support.zoom.us/hc/en-us/articles/207599483-Screen-Share-a-Camera-Inpu
Otherwise here are some hacks to make your own. I wouldn't suggest buying a document camera since they are very expensive.
The first thing that you will need is a surface to write on. Below are a few options.
If you use Zoom then you will have access to their digital whiteboard that you and all of your students have access to.
Even better is joining Zoom with 2 separate sessions, using your computer for Audio and Video, and your iPad or Android table to draw on. You will just need to download the Zoom app on that device.
https://www.youtube.com/watch?v=SCr010CMRsg
If you are not using zoom and instead using Screen Recording software to save and share with your students There are several free options for you to explore. Khan from Khan Academy uses