In a small bowl, whisk together the salt, spice mix, and olive oil to make a viscous paste. On a small sheet tray, rub the lamb with the rub and let it sit, covered, at room temperature for 2 hours or marinate in the refrigerator overnight.
If the lamb has been marinated overnight, remove it from the refrigerator 1 hour before cooking to bring it to room temperature.
Preheat the oven to 350°F.
Pour the neutral oil into a cast-iron skillet or heavy pan and warm over medium-high heat. When the oil is hot, sear the lamb, browning each side for about 3 minutes or until a deep golden char is achieved. Cover the pan with aluminum foil and bake for 1 to 1½ hours or until the meat softens and easily pulls away from the bone.
Once cool enough to touch, pull the meat from the bone, coarsely chop it into bite-size pieces, and shred the pieces into strands. Reincorporate the juices and rendered fat into the pulled chopped meat.
Just before serving, reheat the cast-iron skillet and crisp the lamb, pressing the strands with a spatula, browning the bottoms and then flipping the meat to do the same on the other side. You should have a varied texture with a mix of crispy and soft pieces.
When ready to serve, scoop the Chickpea-Tahini Spread onto a plate or into a shallow bowl. Use the back of a spoon to form a moat between the outer edge and the center. Spoon the hot crispy lamb, along with its juices, into the well and garnish with a bit more oil and spice mix.
The lamb can be stored in an airtight container in the refrigerator for up to 3 days.