Put your mixing board, computer interface, tape machines and outboard rack gear in place, where they will remain, before you start designing the patch bay and wiring.
Decide where you would like your patch bay to be located. Locate it near the mixing board because you will be sitting there most often, and work more efficiently. The mixer will also have the most connections to the patch bay, so you will have shorter cable runs, thus cleaner and cheaper ones.
Draw a map of the studio layout where you can map out necessary cabling and lengths.
Make a list of your equipment. Include the amount of inputs and outputs for each piece of equipment.
Measure the distance from the patch bay to the inputs and outputs of each piece of gear. Leave enough slack (around 2' on each end) to pull gear out of the rack for maintenance, and to pull the patch bay out of the rack for soldering repair.
Add up these totals for the total amount of wiring you will need. If you want, you can plan to gather groups of inputs and outputs for equipment near one another into "snakes," or multichannel bundles of wire. You can make these by using cable ties to group the wires, or buy them in many different configurations and lengths.
Note individual cable lengths and total cable length needed on your studio map and equipment list.
Look at the connectors for the inputs and outputs for each piece of equipment in your studio. Most will be either XLR (male or female), 1/4" (balanced or unbalanced) or RCA. Consult the manual if there is a question about whether a piece of equipment is balanced or unbalanced.
Count the total amount of inputs and outputs you will be using.
Choose which patch bay type and how many you will use based on the amount of rack space you have, the amount of inputs and outputs you need to interconnect and what your personal preference is. The two main types to choose from are TT and 1/4". 1/4" have 48 1/4" jacks on the front (two rows of 24). TT have 96 smaller jacks in the front (two rows of 48). Each unit is two rack spaces high.
Add the required connectors for each piece of equipment onto your equipment list. You can use this later to know how many of each connector you need to buy.
Draw the front panel of the patch bay on paper, using the proper amount of jacks based on what type of patch bay and how many units you decide to use.
Lay out the inputs and outputs of your equipment on the front panel drawing. Put inputs on the top row and outputs of the same gear directly underneath, on the bottom row, of each patch bay unit. You can reverse this is you want to, but be consistent.
Based on this design, figure out what lengths of cables need to go from the back of each point on the patch bay to their respective piece of gear in the studio. Note this on your paper.
Look at your equipment list. You should now be able to see which pieces of gear need which lengths of cables based on where they're located, and which kind of connectors they each need.
Think about the normal, everyday flow of your studio. If there are pieces of gear that will normally be connected together, decide whether you would like to normalize or half-normalize gear together on the patch bay. This means that when no cable is inserted into the front jack of the patch bay the connection is made between two pieces of gear automatically. When a cable is inserted it either breaks the connection (normalized) or does not (half-normalized). Either way the signal will be routed to the inserted cable (see Resource 1 for more information on this).
Write down the pieces of gear you want normalized together (for example: the outputs of your D/A converter normalized to the inputs of your mixer) and which patch points these occupy so you know how to interconnect them later while soldering the patch bay.
Estimate how many patch bay cables you will need based on how many interconnections you will need to make in your everyday work flow. Buy the correct type (TT or 1/4"), and long enough cables to easily stretch the entire patch bay to connect equipment on opposite ends.
Decide how you would like to label the front of your patch bay. You can simply use tape written with pen or make a template in a word processing program and print it out. New patch bays sometimes come with their own self-adhesive labeling.
Order the necessary patch bays, wiring, connectors and patch bay cables. If necessary, source some of these items used on online audio forums, but know that used patch bays might have solder points that need to be cleaned, or cabling already attached to it that needs to be removed.