In a medium bowl, combine the oats, 3/4 cup flour, brown sugar, ginger, and salt. Pour in the melted butter and stir until it forms clumps and the dry ingredients are evenly moistened. Set aside 1/2 cup of the crumble mixture, then press the rest into an even layer in the bottom of the prepared pan.
Place a rack in the center of your oven and heat to 375 degrees F. Line an 8-by-8-inch baking pan with parchment paper so that the paper overhangs two sides like "handles."