Goal clearances are a distinctive part of Futsal and very different to a goal kick in football.
The major distinction is the fact that the goalkeeper must release the ball with their hands from the penalty area.
Some common mistakes made in goal clearances are when a goalkeeper extends their arms beyond the penalty area line when releasing the ball. This is constituted as an improper restart and so the goal clearance must be retaken.
The only note is that the 4-second count for the restart does not reset; it continues. This leaves the possibility to lose possession from the 4-second count running out. If it does, an indirect free kick would be awarded to the opposing team.
On a side note, during general play, extending the hand with the ball over the penalty area line is a direct free kick offence and an accumulated foul. This constitutes deliberate handling much like football.
Also during general play, the goalkeeper is allowed to drop kick the ball and score directly on the opposing net.
Some new goalkeepers to Futsal, when taking a goal clearance, tend to strike the ball as it rolls to them (from being returned to them from out of bounds). This is, demonstrated below is an improper restart as well.
The goalkeeper must also deliver the ball with the hands from within the court with both feet inside (not outside as below).
Lastly the ball must exit the penalty area in order for the ball to be considered in play so an opponent or teammate may not touch the ball until then. The referee must continue counting until the ball is in play.