Preheat oven to 350.
In a large bowl combine oat flour, almond flour and coconut flour with a pinch or so of salt. In the same bowl, add maple syrup, coconut oil and vanilla. Mix until fully combined.
Transfer 3/4 of the mixture to a parchment lined 9x9 baking dish. Press and make sure that the mixture is even on the bottom of the dish. Bake for 15 minutes.
While the base is cooking, add frozen strawberries to a saucepan over low/medium heat. Once they start to soften, mash them down a bit with either a fork or a potato masher. Add maple syrup, tapioca starch, chia seeds and lemon juice and stir gently for a few minutes until the mixture thickens.
Once the base is finished cooking, it will be set but not golden brown.
Pour the strawberry mixture over the top. Wiggle the pan around a bit to ensure that the strawberry mixture is evenly distributed.
Take that 1/4 of the base that we saved from before and crumble over the top of the strawberry mixture.
Place in the oven for its final bake and bake for about 20-25 minutes.
Let cool completely before cutting into bars.
I like to refrigerate mine because I think they taste extra yummy chilled and they last longer but you can also store them in an airtight container at room temp for about 3 days.