1. Coat two 9-by-5-inch straight-sided loaf pans with cooking spray. Line with parchment paper by cutting two strips for each, one the width and the other the length of the pan, and overlapping them inside the pans (make them long enough to generously hang over edges of pans).

2. Beat coffee ice cream in the bowl of an electric mixer fitted with the paddle attachment until soft but still holding its shape, 1 to 2 minutes; work in batches if necessary. Spread ice cream into one of the prepared pans to about 2 inches thick; smooth top with a small offset spatula. Transfer pan to freezer; let ice cream solidify, about 2 hours. Repeat process with praline ice cream, filling remaining pan. Freeze ice cream until it hardens, about 2 hours.

3. When ice cream has hardened, remove pans from freezer. To unmold, dip pans into very hot water for a few seconds; invert onto a cutting board. Remove parchment. Working quickly, cut each block lengthwise into two long equal-size square logs. Using a long spatula, transfer the pieces to a piece of plastic wrap. Stack them on top of each other, alternating colors, to form the checkerboard. Wrap quickly in plastic; return to freezer to chill. When checkerboard is hardened, about 2 hours, remove from freezer; unwrap onto a clean cutting board sprinkled with sliced almonds, if using, to keep ice cream from slipping. Slice crosswise into 12 pieces, and transfer to a serving tray or plates.