At this point, you can proceed one of two ways. If you started with not-too-juicy tomatoes and you have a few large sheet pans, you can directly pour the tomato pulp onto one or two large rimmed baking sheet(s) and bake in a preheated 300°F oven for about 3 hours.
If your tomatoes were juicier or you don't have a large enough rimmed baking sheet, feel free to boil down the tomato purée on the stove first. Reduce it by up to one-third (or even one-half if your tomatoes were super juicy) by bringing it to a simmer and maintaining a steady simmer until the tomatoes have reduced. Then, you can pour this more concentrated tomato mixture onto a rimmed baking sheet or smaller roasting pan to finish reducing it in the oven. (While it is possible to reduce it entirely on the stove, it's tricky business to get it to the right consistency without burning it. I vastly prefer to make it in an oven.)