To add sockets in Diablo 2 Resurrected with the Horadric Cube, the first step is to actually get the thing, as we cover in our Horadric Cube guide.

How to Add Sockets with the Cube – Diablo 2 Resurrected For 4 socket shield you will have to wait until Hell difficulty to get white Monarch shield to drop. These can be high enough level (item level 26 to 40) to get full 4 sockets. There are normal white crystal swords that can drop in Act V on normal difficulty. Because of this for most weapons and shields that can have 4+ sockets created by Larzuk you will have to wait until at least Nightmare difficulty Act I. Level of the item on the other hand depends entirely on the level of the monster that dropped it.

Number of sockets an item can get depends entirely on the level of the item. What this means is that you have to get white items to drop from high enough level monsters. White and Gray items – Maximum amount of sockets based on item level, calculated based on the level of the monster that dropped it, which scales with difficulty.Magic items – one to two sockets, at random.

Diablo 2 rune socket recipe