We put a cross-brace in the cabinet between the woofer and tweeter horn. It spans front to back and side to side. It is usually made from wood falloff, scrap material left over from cutting out the cabinet. You can also use solid 1x2 wood stock or something like that.The port is also made from the same wood that the cabinet is made from. It is like an internal box open at the baffle and through to the inside of the cabinet. Make sure the dimensions are right, and the 10" length is from the front of the baffle to the exit inside the cabinet.
Other than that, it's a simple cabinet to build. As long as it is structurally solid and doesn't have cracks at the seams, it will work fine.