It doesn't take very long before you have filled up all available weapon slots in Breath of the Wild. Once this happens, you will need to start deciding what weapons you want to leave behind when you find something new. This can be frustrating when you already have an inventory full of good weapons. The logical question here is can you get more weapon slots?
The answer is yes. On your way to Kakariko village, you will come across a large tree like person called Hestu, who will give you a quest to obtain his Maracas. Once you do this you will unlock the ability to purchase new inventory slots for all of the categories that have limitations, such as weapons, shields, and bows.
To purchase a new weapon slot, you will first need to find a Korok Seed. These can be found all over Hyrule. You will be awarded one for finding a hidden Korok. They are fairly well hidden, but if you keep your eyes open for something out of the ordinary, it's likely a Korok and once you speak to him he will give you a seed.