Place chicken thighs in a single layer in a non-reactive dish. Combine salt, spices, thyme and bay leaves in a bowl, mix well, then scatter over chicken, turn to coat, cover and refrigerate while the flavours develop (1 hour).
Preheat oven to 160C. Remove chicken from salt, rinse under cold water and pat dry with absorbent paper. Place in a single layer in a large casserole, cover with canola oil and 500ml olive oil and cook in oven until tender (1½-2 hours). Remove from oil with a slotted spoon (discard oil), set aside to cool.
Meanwhile, for grain salad, preheat oven to 200C. Combine chickpeas with cold water in a saucepan, bring to the boil over medium heat and cook until tender (40-45 minutes), drain and set aside to cool. Meanwhile, cook rice in a saucepan of boiling water until tender (20-30 minutes), drain and set aside to cool. Meanwhile, toast farro in a saucepan over medium heat, stirring occasionally, until fragrant (2-3 minutes). Add 250ml water, bring to the boil, cover, reduce heat to low and simmer until grains are tender (15-20 minutes). Remove from heat, stand for 5 minutes, then cool completely. Combine with chickpeas and rice. Roast dates on a baking tray until crisp (2-3 minutes), coarsely chop and add to remaining ingredients, season to taste and set aside.
Roast pancetta on a tray lined with baking paper until crisp (3-5 minutes), drain on absorbent paper and set aside.
Heat remaining olive oil in a large frying pan over high heat, add chicken and cook in batches, skin-side down, turning once, until golden and crisp (2-3 minutes). Transfer to a baking tray and roast until warmed through (5-7 minutes). Spoon yoghurt onto serving plates, scatter with sumac, coriander seeds, pistachios and mint, top with grain salad and chicken and serve.