Slice tomatoes as uniformly as possible to a maximum of 1/4" thickness. and lay them out on a cookie sheet in a single layer.
Heat your oven to a low temperature. You can potentially set it from 160 up to about 255 Fahrenheit, but I recommend going with the lowest possible temperature to prevent burning.
Drizzle a small amount of olive oil over them (optional) and sprinkle lightly with salt.
Season with spices if desired.
Place baking sheets into the oven and bake, watching them carefully so they don’t burn. They'll be in there for a while--possibly all day.
If desired, flip tomatoes in the middle of the drying time (around the 3 hour mark) to make them dry a bit faster.
The tomatoes are done when they are dry but still pliable (not moist or sticky).
Technically, you can dry the tomatoes more than stated--they will be a lot less pliable or even not pliable at all. It’s a matter of personal preference, but I love them both ways! The more dry they are, the longer their shelf life will be.TO MAKE SUN-DRIED TOMATOES IN A DEHYDRATOR:Instead of using baking sheets, use dehydrator trays. Dry at 125 degrees Fahrenheit until tomatoes are dry, but still pliable.TO MAKE SUN-DRIED TOMATOES IN THE SUN:Place tomato slices on some kind of raised screen to dry in the sun. Cover with cheesecloth. See post for more information including drying supplies.