I have two "locked" weapon slots. How can I unlock them?

Are the accessory slots locked too? Do they have some sort of level requirement?

2 Answers

They're obtained in parts of the main story; one in the early Sanctuary missions and one is unlocked :

when you get back to Sactuary after it takes off. If I remember correctly.

The Relic/Class Mod/Grenade Mod/Shield slots are only locked during the tutorial, they're unlocked extremely early. You never have to do anything but complete story missions to unlock the slots.

You get your first weapon slot upgrade upon finishing the mission where you get the message from Roland in Sanctuary.