Print top and bottom parts. 3 perimeters, 3 solid top and bottom layers, and 30% infill for studiness.
Adhere your control borad to the case bottom with some double-sided foam tape. Assembly the two case halves with #4 X 5/8" wood screw or just zip-tie the holes.
If you have altitude holding issues, you can try putting a small cotton or poly stuff ball over the barometer.