I've finally moved past my many trials of deodorant testing (and used up the last of the cornstarch and baking soda mix).
Just baking soda works well, but is a bit scratchy. The powder also ends up on the floor, sheets, etc. It was still worth the trouble to avoid the store-bought deodorant.
Mixing the baking soda with cornstarch made it feel softer and smoother, but the powder is still messy. It was still worth it.
I found coconut oil on sale at my favorite store - Sprouts. I got a couple containers just for this purpose. Now I know it's a healthy oil for eating, but when I bought it a couple months ago, I had the purpose of making deodorant in mind.
This is the recipe (and baby steps I copied in my own personal experiment) at kitchenstewardship.com
I shoved it into a deodorant container. This works well, but is a bit more solid than I anticipated at the really cold winter temperatures in Colorado. To put this in perspective, I drop my heat down to 57 while we're sleeping since we're sleeping, bundled in warm blankets and fuzzy pjs. The warmth of Phoenix is a bit too warm to keep it in a deodorant container because it turns into a liquid. This is not just a little mushy, but complete oily liquid. I decided to go with a small container with a lid to store mine in, just in case it gets warm and I am unaware. I love it. It feels more like normal deodorant. It's not scratchy. It doesn't leave little bits of white powder on things. It feels nice, soft and moisturizing. I smell better too. Fabulous stuff this homemade deodorant is!