How to videos
If you want to make your own pads, there are lots of resources online. Youtube videos and patterns free to community groups and for self use. If you make pads to sell, please buy the pattern rights as well as inform the designers that you are using their patterns.
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How to make your own reusable sanitary pads | Period Poverty | ActionAid UK
This video shows a simple way of how to make pads by hand. It is suitable for beginners and for using scraps. You can also adapt this to machine sewing if you like the concept.
Making pads for the Pachamama project
This video from a project that makes pads for refugees is a good explanation on how to make exposed core pads.
How to draft a symmetrical pad pattern
If you like to make your own pattern, this video explains how to best make it.