Make sure you have the right style case: Many of the smaller injection molded and aluminum carry cases come standard will molded-in panel tabs sets down a short distance from the lid split. This is not true for luggage style cases that are either soft-sided or thermoformed. It is not recommended that you use luggage style cases for panel mounted equipment. Some larger cases (think airline check-through size) also have panel tabs in them. For larger hard cases without stock panel tabs, a workable system can still be constructed, but you will most likely need the assistance of a case professional.
Choose the right panel material: The two best options are ABS plastic and aluminum plate. Plastic has distinct advantage over aluminum in that it is less expensive, lighter, more malleable, and it is easier to route or cut. When using plastic, you will most likely need at least .125”of panel thickness, and up to a .25” thickness for very large panels or heavy items. Aluminum panels can be .0625” to .125”. If you feel that you need more than .125” of aluminum panel thickness to hold your equipments weight, this is a good indication that you should reconsider panel mounting it, and should consider other options such as a custom cushioned case interior.
Decide how you are going to cut the panel material: There are several options here. A small hand router may be all you need for basic round or square holes. This will obviously be harder with thick aluminum, but it will be fairly easy for a good craftsman to do with plastic. If you need a very sharp appearance, or exact cuts, you should hire a waterjet cutting outfit, or find someone with a CNC router. Some engravers will be able to not only cut your required holes, but will also be able to route in descriptions under each item by using a two-tone plastic. This is the same process used in engraving your name on the bowling trophy you got 10 years ago!
Decide how you are going to secure your product to the panel: Most mounting equipment comes with its own screws and screw holes. If yours does not, you will need to find a place to drill a through-hole. The best way to secure the item to the panel is by inserting a threaded insert into the plastic or aluminum,, and then screwing into it. In using plastic, you can accomplish this by carefully holding the insert over its intended pre-drilled hole, and heating it up with a soldering iron until it melts down into the plastic. Sounds easy, but you may want to practice this before you start on your actual panel. You will need an insert puller in order set these into aluminum.
Securing the panel to the case: If your case manufacturer make a standard panel ring, you should definitely use it. It should have pre-drilled holes that have threaded inserts already in them. In this case, all you need to do is use a plastic adhesive to glue the panel ring into the case, and then screw the panel to the ring. If your case does not have an OEM ring, or some other type of pre-threaded securing system, you should seek out a case professional for help.
Ventilation and Power Source: If you are operating your items inside the case, you will want to make sure you have ventilation holes cut into the panel on both sides. For extreme heat build-up situations, you will need to use electric fans mounted on either side of the case base. Unfortunately, these fans stick out from the case wall, and are prone to damage. Other than that, they do a good job of moving air. Note that if you route through the case walls to attach fans or power supplies, you will be invalidating the OEM warranty. It is a good idea to use a professional case builder here, since they will most likely warranty the work they perform above and beyond the OEM warranty.