Blend the watermelon,lemon paste and orange extract in a blender until it’s completely blended into a juice. The watermelon may foam a bit, that’s fine.
Pour into a 9-inch bread pan or deep baking dish, cover and freeze for at least 4 hours, overnight is best. Scrape the frozen juice with the tines of a fork until the frozen mixture is light and flaky, like shaved ice. Freeze again if it begins to melt.