I was here to make this same comment. My oven has halogen lights, and with just the light on, it gets to about 120 degrees F inside. You could also set it at the lowest setting and leave the door cracked a bit. Or if you're really committed, you could turn the oven on every once in a while, let it start to heat up, and then turn it back off, just to keep it warm. Dehydrating in the oven is a lot easier for things like jerky that can take a bit more heat. With garlic, I would imagine that too much heat would give it more the flavor of roasted garlic rather than fresh, raw garlic. Which would also be lovely, but might not be what you're going for.
If I wanted to do this and didn't have a dehydrator, I'd probably put thinly sliced garlic on parchment paper in the oven with the heat off but the lights on and let it stay there for a few days until it was nice and crispy. I think you'd be successful with that.
Of course, you were asking this question over 5 months ago, so you have probably already experimented. Maybe you will come back and say what your experiences were!
I was here to make this same comment. My oven has halogen lights, and with just the light on, it gets to about 120 degrees F inside. You could also set it at the lowest setting and leave the door cracked a bit. Or if you're really committed, you could turn the oven on every once in a while, let it start to heat up, and then turn it back off, just to keep it warm. Dehydrating in the oven is a lot easier for things like jerky that can take a bit more heat. With garlic, I would imagine that too much heat would give it more the flavor of roasted garlic rather than fresh, raw garlic. Which would also be lovely, but might not be what you're going for.
If I wanted to do this and didn't have a dehydrator, I'd probably put thinly sliced garlic on parchment paper in the oven with the heat off but the lights on and let it stay there for a few days until it was nice and crispy. I think you'd be successful with that.
Of course, you were asking this question over 5 months ago, so you have probably already experimented. Maybe you will come back and say what your experiences were!