In a bowl, mix together the gluten-free oats, almond flour, brown sugar, melted coconut oil, honey, vanilla extract, baking soda, and salt until well combined.
Drop spoonfuls of the mixture onto a baking sheet lined with parchment paper.
Bake for 10-12 minutes or until the edges are golden brown.
Let the cookies cool completely on a wire rack.
In a separate bowl, beat together the powdered sugar, softened butter, and vanilla extract until smooth to make the filling.
Spread the filling on the flat side of one cookie and top with another cookie to form a sandwich.
Repeat with the remaining cookies and filling.
Notes
Store in an airtight container for up to a week.
Feel free to add chocolate chips or nuts to the cookie mixture for extra flavor.