Take the flank steak out of the refrigerator and let it warm up a little as you get started on the potatoes. Don't put any salt on the meat until just before you are going to put it on the grill. The salt will draw a lot of the moisture out. Heat the grill - or skillet - up to medium high. Rub it with some cooking oil. Slice the potatoes up and put them in a bowl. Drizzle with some EVOO and sprinkle with some salt, pepper and powdered garlic. Stir things up until all the slices are coated. Put the salad together while the potatoes and meat are cooking. The thinner the potato slices the faster they will cook. About 3/8" works best for me.
Spread the potato slices out on the grill. When they are showing the grill marks turn them over. Salt, pepper and garlic powder both sides of the steak and lay it on the grill. Depending on how thick it is and how done you like it - 2 to 7 or 8 minutes a side. To test it for how well done it is poke it and if it is soft it is rare. If it is starting to get firm but still a bit soft in the middle it is medium. If it is firm it is well done. Remember you can always cook it some more but you can't "uncook" it.
When the steak is done the way you want it remove it to a large platter that will catch the drippings and let it rest for at least five minutes before you slice it.
Slice it across the grain and top it with a little bit of the drippings when you serve it. Grilled Flank Steak and Potatoes. Enjoy!