I have an existing GFCI outlet under my sink dedicated to my dishwasher. I want to add an outlet next to the GFCI that can be controlled by a switch for my garbage disposal. There is 14/2 wire running into the receptacle with the GFCI. I pulled some 14/3 from the switch to the same receptacle to control the new outlet. I attached a picture to give an idea of what I'm talking about. The power coming in will connect to the line side of the GFCI. The run the neutral and hot out of the load side to the outlet. I'm not sure how to incorporate the switch. I would appreciate any guidance.
In the simplest solution, a cable goes from the GFCI to the switch box, and another from the switch box to the outlet. At the switch box, white goes to white, ground to ground, and one black goes to each of the switch terminals.
If this is impractical, the wiring can go from GFCI to outlet box, and a second cable goes from outlet box to the switch. This is a bit more complicated and I'm not up for describing it again right now; search past answers for "switch loop".