Usually I prefer to roast a large boneless leg of lamb, but there's also a time and a place for smaller pieces or even individual chops. If you know that timing is going to be really really tricky, this might be your best bet...it won't hurt the dish at all to stay in the oven longer. The meat and potatoes will just keep getting more tender.
Braised Lamb with Potatoes (Greek style)
1 c fresh lemon juice (from 4 or 5 lemons)
1/2 c olive oil
3 T fresh oregano or 1 T dried
Coarse salt and freshly ground pepper
2 lbs of lamb, chops, chunks, or leg slices
2 lb Yukon Gold potatoes, cut into quarters
Combine lemon juice, oil, oregano, salt and pepper in a zip loc bag. Add lamb to marinade, turning to coat well. Refrigerate 24 hours, turning a few times.
Place lamb and marinade in a roasting pan, adding water if needed to come up about half way on meat. Cover pan tightly with foil and roast at 300 for an hour or more. Flip lamb and add potatoes. Roast for another hour or more. Uncover and roast at 400 to brown the potatoes.