Add the frozen strawberries, strawberry preserves, lemon juice, vanilla, ground flaxseed, maple syrup, and salt to a high-powered blender.
Blend until completely smooth. If the mixture struggles to blend, add a small splash of water, just enough to help everything move without thinning the sorbet too much.
Depending on your blender and the temperature of your berries, the sorbet may already be thick enough to enjoy immediately as a soft-serve style dessert. For a firmer texture, pour the mixture into a shallow freezer-safe container and freeze for 2 to 3 hours, or until fully set.
Once frozen, let the sorbet sit at room temperature for a few minutes before scooping for the best texture.