Design the Pantry
If you want to incorporate special areas to consolidate electrical charge items (such as cell phones), you might want to consider rerouting electrical plugs. This is essentially lengthening the wire of the original outlet and threading it around/up through the wall to a new opening you create. Make sure to cut off the flow of electricity to that outlet before making any changes to the wiring. If you don't feel comfortable doing this, find a professional.
When building with plywood, keep in mind using any measurement of 4' (or a multiple thereof) comes in quite handy because a standard sheet of plywood is 4' wide. Being able to create something using a standard measurement minimizes the amount of cuts you have to make, which lessens the amount of wasted wood.
Once you know the size of your unit, measure out and mark your cuts on the plywood and use a table saw to cut out the pieces. The pantry in this project measures approximately 24" deep x 45" wide x 9' tall. At this point, decide whether you're going to want external cabinet doors; if so, you will need to plan for them and cut them.
If you rerouted any electrical, make sure you include those measurements when cutting the plywood for the base of your unit. You will need to make a corresponding cut through your plywood back in order to make use of that electrical source.
If you don't want to cut the wood you can take the measurements to a hardware store and have the lumber cut there.