Final answer:
After hanging the bag, the nurse should open the roller clamp on the tubing to initiate the flow of the feeding solution into the gastrostomy tube.
Step-by-step explanation:
The next step in the gravity feeding process after hanging the bag is to initiate the flow of the feeding solution into the gastrostomy tube. This is done by opening the roller clamp on the tubing to allow the solution to flow by gravity. The nurse should monitor the flow rate and adjust the clamp as needed to ensure a controlled and appropriate rate of infusion.