Whisk together the flours, spices, xanthan gum, baking powder, baking soda, and salt. Set aside.
With a mixer (either stand or hand), beat the brown sugar and the butter at medium-high speed until fluffy.
Add the molasses, bananas, and apple cider vinegar to the butter/sugar mixture and blend until creamy.
Turn the mixer down to low and gradually add the dry ingredients until incorporated into the wet ingredients and a soft dough forms.
Divide the dough into 6 parts. Wrap each portion in plastic wrap and form into a ball. The dough will be sticky. Refrigerate overnight or for at least 6 hours. It will firm up in the refrigerator.
Preheat the oven to 375°F.
Line baking sheets with parchment paper.
Taking one ball of dough out of the refrigerator at a time, place it between parchment or waxed paper, and put it on a board or counter. Roll the dough to a thickness of 1/4" to 1/2". The thinner the cookie, the crispier it will be, but it will be hard to transfer it to the cookie sheet if too thin. If the dough gets sticky before all your cookies are cut, simply put it back into the plastic wrap and refrigerate it as you roll out one of the other balls.
Cut out the cookies with gingerbread people-shaped cutters. Using a thin spatula, transfer the cookies to the lined baking sheets. Adding a little flour on the spatula when it gets sticky will help.
Bake for 9 to 11 minutes. The thicker the cookie, the longer it takes to bake. Bake only until lightly brown around the edges and until slightly firm to the touch. Do not overbake. This results in a dry cookie.
Cool on the baking sheet for 5 minutes before transferring to a cooling rack. Before icing or decorating, let cool completely
Makes approximately 36 cookies, more or less depending on the size of your gingerbread people cutter.
Note: If you want to make your own oat flour, blend 2 cups oats in a blender until reaching a flour consistency.
Xanthan gum is an ingredient commonly used in gluten-free baking. It produces a texture very much like using gluten flours. It also helps to bind ingredients together. Xanthan gum is made from corn. If you have corn allergies, try substituting guar gum.
If you are baking all of the cookies at once, place unfrosted cookies in the refrigerator. Frost only those cookies you plan on serving.