Ingredients to Glass
Bucket of Sand - One bucket makes 1 glass item.
Glassblowing Pipe - This makes the object.
Seaweed - You need one seaweed per bucket of sand.
Making Glass
Firstly, just put all of your weapons and armor into the bank since you can't bring them to Entrana. Buy a bucket or 2 from the General store to hold your sand. If you don't want to wait for seaweed to wash up on the beach of Entrana, you can fish for some with a Big Net in Catherby. There is also a respawn on the northern side of the river that runs through Shilo Village.
Go to Port Sarim and catch the boat to Entrana by talking to the monks.
Get off the boat and go into the house to the north, across from the furnace. Inside will be a glassblowing pipe on top of the dresser. Grab it. Also notice the stove.
If you need to, head over to the beach on the far north-west side of the island and pick up some seaweed.
Go back to the house where you found the glass-blowing pipe and cook the seaweed over the range to get some soda ash.
Fill your bucket of sand up from the sand pit located conveniently near the range and furnace. It's just south of the range and south-west of the furnace.
Use the bucket of sand with the furnace to get some molten glass.
Now use your glassblowing pipe with the glass to bring up a menu of things to make!