4 tablespoons baking soda
2 tablespoons coconut oil (melted to its liquid state) or glycerin
3 teaspoons xylitol
15 drops peppermint oil
Mix everything in a small bowl until it forms a uniform paste. Add more peppermint oil 5 drops at a time, tasting as you go, if you like it stronger. Transfer to a small glass jar or storage container with a tight-fitting lid. The toothpaste will keep unrefrigerated for months.
I've used a washed baby food jar and we use a popsicle stick to get the toothpaste onto our toothbrushes.