so this is a new stick project with new measurement (400mm x 260mm x 50mm) and creative Case Design. But here're the photos from scratch.
Extact work is very important at this stage.
Glue it all together. This corner clamps help to get the right angles.
First Primer will be sanded off with 80 to 120 paper. Then use again primer and sand again with 320. Edges should be filled good enough after this process.