I've seen these nifty mason jar soap dispensers everywhere online...but have yet to create one of my own- so I have put the instructions below, that I found, and plan to use. Maybe you'll also find them useful...
How to Create your own! :
1. First, measure and mark the center of the jar's lid.
2. Using a 1/2" high-speed steel drill bit, drill a hole to fit the width of a soap dispenser pump. You can use the pumps from old lotion bottles, etc.3. Fill the jar with liquid soap, screw the lid back on, and insert the pump. You may need to trim the bottom of the pump to fit your jar. If so, cut at an slight angle.