Position a rack in the upper third of the oven and preheat to 500 degrees F. Put the onions, olives, chiles and bay leaves on a rimmed baking sheet. Cut 1 orange half into wedges and add to the baking sheet.
Evenly space the chicken thighs, skin-side up, on the baking sheet on top of the other ingredients. Drizzle with the olive oil and squeeze the juice from the remaining orange half on top. Season with salt.
Roast until the chicken is cooked through and the skin is crisp and golden, 30 to 35 minutes. Discard the bay leaves. Serve the chicken with the onions, olives, oranges and pan juices.