Line a baking sheet with parchment paper. Spread the softened vanilla ice cream onto the parchment paper in an even layer, about 0.5 inches thick. Freeze until firm, about 1-2 hours.
Once the ice cream is firm, cut it into desired shapes using cookie cutters (stars or squares work well).
Break the graham crackers into pieces that match the size of your ice cream shapes.
Spread a thin layer of whipped cream or frosting onto the bottom of a graham cracker piece.
Place an ice cream shape on top of the whipped cream.
Top with another graham cracker piece and gently press down.
Immediately roll the sides of the ice cream sandwich in red and blue sprinkles, alternating colors.
Place the finished ice cream sandwiches back on the parchment-lined baking sheet and freeze until solid, at least 2 hours.
Notes
For best results, work quickly when assembling the sandwiches to prevent the ice cream from melting.