I need to make a custom enclosure for a project, but I don't know how to machine it. I made a quick 3d model of one half to help explain. It will be made from two blocks of aluminum, with the edges and corners rounded (see first picture) and the inside hollowed out, except for 4 protrusions for screws to go in to connect the two halves (see second picture). Then, a few holes will be drilled, and somehow a rectangular slot will be made (see third picture). I don't have access to a CNC Mill, so how would I make this by hand with high precison?