If a defender throws his shoe at an attacking player inside the goal area, what is the proper restart?

When a defender throws a shoe at an attacking player inside the goal area, this action is considered to be a violent conduct that occurs within the context of a foul. According to the Laws of the Game, any act of serious foul play or violent conduct warrants a penalty kick if it occurs within the penalty area. In this case, the defender deliberately threw an object (the shoe) at an opponent, which constitutes a serious infringement.

Thus, because the act occurred inside the goal area, it leads to a scenario where the attacking team is awarded a penalty kick. The penalty kick allows the attacking team a direct chance to score from the designated spot, reflecting the seriousness of the infringement and the fact that the defender's action was aggressive and against the spirit of the game.