Place the trimmed strawberries in a blender or food processor and puree them for a minute or so until smooth. You don’t want any strawberry chunks in the mixture.
Transfer the strawberry puree to a saucepan and add the lemon juice and sugar, if using. Turn the heat to medium high, and cook the mixture for about 10 minutes, stirring frequently, until the mixture is thick and jammy. The goal here is to cook out much of the moisture.
Preheat the oven to 170 degrees F, or as low as your oven will go, making sure it’s less than 200 degrees at the highest.
Spread the strawberry jam into a rectangle shape onto a baking pan lined with a silpat or parchment paper. You may use an offset spatula or a regular spatula to help spread the mixture as evenly as possible, until the rectangle is about 1/8 inch thick. Keep in mind the fruit leather will lose some of its thickness in the oven as it dehydrates, so make sure that none of the jam is so thin that you can see through it as you spread.
Cook in the oven for 3-4 hours, until the fruit mixture no longer feels sticky, just a bit tacky. Remove from the oven and let it cool completely. Transfer to a cutting board lined with wax paper, and use a pizza cutter to cut long strips. Roll them up into the fruit rollups, and enjoy!