Preheat the oven to 350 degrees F (175 degrees C).
Place one of the pie crusts into the bottom of a 10 inch pie plate or 9 inch deep dish pie plate. Put the rhubarb in the pie shell. In a small bowl, stir together the flour and 2 cups of sugar. In a medium bowl, whisk together the egg yolks, 1 cup half-and-half, and almond extract. Stir in the sugar and flour until well blended.
Pour the sauce over the rhubarb - it may not all fit into the pan, so just discard any remaining mixture. Place the top pie crust over the filling, seal the edges and flute. Brush the top crust with the remaining half-and-half, and sprinkle with remaining sugar. Cut a few small slits in the top crust for ventilation. Place the pie onto a cookie sheet to catch any drips.
Bake for 45 minutes in the preheated oven, or until puffed up in the middle and golden brown on the top. A knife should easily pierce the rhubarb. Cool until just warm before serving to allow the custard to set.
You can use frozen rhubarb, but you will need to increase your cooking time by about 15 minutes.
Do not substitute fat-free half-and-half. I have, and the flavor is still good, but the consistency was runny.