Preheat oven to 350°F.
Spread the coconut on a baking sheet. Toast 2-3 minutes. Remove from the oven and allow to cool. Keep your eye on it as coconut will brown quickly
Grease a 9"x 13"x 2" baking pan. Line the bottom with parchment paper.
In an electric mixer on low speed, mix the flour, brown sugar, granulated sugar, and salt until combined. Add the butter and continue mixing until the dough begins to come together. Stir in the coconut and oats.
Remove 3/4-1 cup of the crust dough. Set aside. If adding optional ingredients remove 3/4 cup of crumble.
Pour the remaining dough to pan. Press evenly into the bottom of the prepared pan, I use a flat bottom cup to press dough into pan. Bake 14-17 minutes, rotating the pan halfway through baking. The crust should be golden brown around the edges. Allow the crust to cool for 10 minutes.
Spread the preserves evenly over the crust, leaving a scant 1/2-inch border. If you are adding nuts or dried fruit, sprinkle on preserves now then crumble the reserved dough over the top. Bake 7 minutes, or until the preserves are bubbly. Cool completely in pan.
Run a knife around the edges of the bars. Place a baking sheet on top of the pan and flip the pan over to release the bars. Peel the parchment paper off. Then flip again. Using a sharp knife, cut the bars into squares, which in a 9x13 won't be exactly squared, lol.