Now that the glue is set, remove the tape and you box is ready for sanding and finishng. When setting your hinges, don't forget your masking tape. Tape the lid to the body and install the hinges to the temporarily assembled pices for a perfect alignment. You might want to add a layer or two of tape along the top-to-bottom joint if you are pre-fitting the hinges before finishing. That way, you build in a slight gap to accout for the finsh thickness and your lid will close without pinching the hinge edge.
If you were careful in your cutting and assembly, once the edge is sanded, the joint will be invisible.
This safe and easy version of miter cutting (aka beveling) is great for beginners. The technisue I typically use is in production work is this one:
I made it at TechShop www.techshop.ws