How to Make It
Preheat the oven to 375°. Line a large rimmed baking sheet with parchment paper. On a large, lightly floured work surface, roll out the pastry 1/8 inch thick. Using a pizza cutter or sharp knife, cut out two 12-by-3-inch rectangles and brush off any excess flour. Transfer the rectangles to the prepared baking sheet. From the remaining puff pastry, cut four 12-by-1/4-inch strips and four 3-by-1/4-inch strips. Moisten the border of the rectangles with water. Lay the long strips on the long edges of each rectangle and the short strips on the short edges of each rectangle; press lightly to seal. With a fork, prick the bottom of the pastry shells all over. Freeze the pastry shells for 15 minutes.
Bake the pastry shells for about 30 minutes, until browned and crisp and the borders have risen nicely. If the centers start to puff up, gently tamp them down with a fork during baking.
Meanwhile, in a large skillet, heat the olive oil. Add the garlic and cook over moderate heat for 30 seconds. Add the onion and cook until softened, about 7 minutes. Add the bell peppers, cover and cook, stirring a few times, until the peppers are tender, about 8 minutes. Uncover and stir in the pimentón. Cook, stirring, for 3 minutes. Add the crab and cook, tossing gently, until heated through, about 3 minutes. Season with salt.
Spread the crab filling into the center of each pastry shell. With a serrated knife, cut the pastry shells crosswise into 12 slices each. Arrange the slices on a platter and serve.