This is the step that's easiest to overlook and most expensive to fix later. Plan your utilities before the cabinetry is built.
Water: The sink needs hot and cold supply lines and a drain. The ice maker needs a cold water supply line of its own. If your station is close to the kitchen, you may be able to tap into existing plumbing. If it's in another room, budget for new lines.
Drainage: Ice makers produce meltwater, and it needs somewhere to go. If there's no floor drain nearby, choose a model with a built-in drain pump. It pushes water up and out to the nearest drain line, including the sink's. ZLINE's Touchstone ice makers are available with drain pumps for exactly this reason.
Power: Every appliance at the station needs an outlet. Confirm the electrical requirements on each spec sheet early. Ask your electrician whether the ice maker should be on its own circuit.
Ventilation: Undercounter appliances designed for built-in installation vent from the front, which is what allows them to sit flush with cabinetry. Check each unit's installation guide for required clearances before finalizing the cutouts.
Bring your contractor, plumber, and cabinetmaker into the same conversation before anything is ordered. A station that's planned on paper installs cleanly. One that's improvised usually ends with an extension cord.