My oven has a dehydration setting, which is what I used for my first batch, but it was not very successful: even after 24 hours the tomatoes weren't dry and I wasn't impressed at having to leave the oven on for so long. (I did learn that my oven automatically turns itself off after being on for 12 hours, so that was vaguely interesting.)
So, Plan B. Which involves the sun. Much more satisfactory.
My set-up is about as low-tech as it gets. Small tomatoes, cut in half and arranged on a baking tray in the greenhouse. I've put the tray on top of some small plant pots - thinking this might deter crawling insects - and I have loosely wrapped horticultural fleece over the tray. The fleece allows the sun through, while letting moisture evaporate off. It also stops flying insects landing on the tomatoes.
They've only been out there for eight hours and are already looking drier than the first batch did after 12 hours in the oven.