Adjust oven rack to lower-middle position and heat oven to 300 degrees.

Cut meat from bones and reserve bones. Trim meat of excess fat and cut into 1 ½-inch cubes. Season meat generously with salt and pepper.

Heat 1 tablespoon oil in large ovenproof Dutch oven over medium-high heat until shimmering, about 2 minutes.

Add half of meat to pot so that individual pieces are close together but not touching. Cook, without moving, until sides touching pot are well-browned, 2 to 3 minutes.

Using tongs, turn each piece and continue cooking until most sides are well-browned, about 5 minutes longer.

Transfer meat to medium bowl, add another 1 tablespoon oil to pot, and swirl to coat pan bottom. Brown remaining lamb; transfer meat to bowl and set aside.

Reduce heat to medium, add remaining tablespoon oil, and swirl to coat pan bottom.

Add onions and ¼ teaspoon salt and cook, stirring frequently and vigorously, scraping bottom of pot with wooden spoon to loosen browned bits, until onions have browned, about 8 minutes.

Add flour and stir until onions are evenly coated, 1 to 2 minutes.

Stir in 1 ½ cups of water, scraping pan bottom and edges with wooden spoon to loosen remaining browned bits.

Gradually remaining 1 ½ cups water, stirring constantly and scraping pan edges to dissolve flour.

Add thyme and 1 teaspoon salt and bring to simmer.

Add bones and then meat and accumulated juices. Return to simmer, cover, and place in oven. Cook for 1 hour.

Remove pot from oven and place carrots and turnips on top of meat and bones.

Cover and return pot to oven and cook until meat is tender, about 1 hour.

If serving immediately, stir carrots and turnips into liquid, wait 5 minutes, and spoon off any fat that rises to top.

(Stew can be covered and refrigerated for up to 3 days. Spoon off congealed fat and bring back to simmer over medium-low heat.)

Stir in parsley and adjust seasoning with salt and pepper.

Remove bones if desired. Serve immediately.