Do you need a prep sink? If it will be used mostly for filling pots or teakettles, a pot-filler may do the trick. It will be a long-armed, cold-water-only faucet that extends from a wall to fill a pot and can be pushed out of the way, when not in use.
This sink should be close to the cooktop and next to the main prep surface, but the position also depends on how you cook and how many cooks you have in the kitchen. There should be enough rooms for trash receptacles near food prep stations.
The prep sinks are splurge that pays the cook back in convenience. It can be used to just rinse fresh produce and put them straight into a waiting pot or pan on the cooktop. There are some undermount stainless-steel prep sink which are deep enough for serious washing. A metal rack helps prevent dishes from breaking.