Making yogurt is really easy. So much so that I rarely (except when I need new starter or I have a run of brain flatulence and forget I need some) buy it. From late fall to late spring, this is my favorite yogurt maker:

In the summer, it goes in the greenhouse. Between those times, this is my second favorite yogurt maker:

(using it for beans at the moment – use the yogurt setting for yogurt).
When you think of fermented foods like yogurt, remember that you are TRYING to grow bacteria (only the right kind), so you want to keep the food (yogurt, kraut, kombucha) at a warm room temperature to encourage that growth.
To make yogurt, I take about 2 tblsp of store bought yogurt (I prefer just plain or vanilla flavored) and put it in a very clean wide mouth quart jar. Then I heat a little less than a quart of milk to almost boiling. It needs to be at least 180* to kill any undesired bacteria that will make your yogurt spoil. Then let the milk cool until it is cool enough that you can leave your hand on the bottom of the pan comfortably. Add it to the mason jar and stir well. Screw on the lid.
Set your yogurt in a warm area (wood stove, greenhouse, front porch in the summer) for at least 8 hours (or use the instant pot). It should be solid-ish at that point. Smell it. It should smell slightly sour, like yogurt. Sometimes, I mess up and the yogurt ends up weird or thin.

Looks gross, I know, and it is very runny. You can fix this – just add some instant dry milk, or strain it with a coffee filter and pour off the whey (liquid part). Or you can use it like this. I used part of this to start some sourdough starter and will use the rest of it in baking or smoothies.
At this point, put it in the fridge. After it’s chilled a while, it will get thicker. You can make it into a cheese-like spread or custard style yogurt.
For custard style yogurt, mix 1 small package of jello (lemon or strawberry is really good) with a cup of boiling water. Let it cool, then stir in 3 cups of yogurt. It will set up kinda like Jello – thicker than plain yogurt. So, so good!
I buy a quart of yogurt (preferably on sale), then freeze it in ice cube trays. 2 cubes is enough for one quart of yogurt. If I pop the cubes into the quart jar, by the time the milk has heated and cooled, the cubes are thawed enough to mix in well.
It’s really important to not over heat the yogurt. If you do, you will kill the bacteria that makes it yogurt. You can use your homemade yogurt for starter, but after a few times, it seems to not set as well and the taste is just funky.
Try making some when you have a chance. You don’t need special equipment, just a place for it to stay consistently warm. A crock pot MIGHT work, but only on a ‘keep warm’ setting. Even the low setting is too warm for yogurt.