Guardians of the Rift

The Guardians of The Rift minigame is great way to craft runes on a UIM. You will craft all types of runes here (excluding souls, wraths, astral, sunfire) but there are some that are locked behind quests. Law runes are locked behind Troll Stronghold, cosmic runes Lost City, blood runes Sins of The Father, death runes Mourning's End II.

If at the end of the game while the portals are being kept open, and you were unable to use the charged guardian essence to charge The Great Guardian preventing you from going to the altar one last time, you can right click and destroy it.

The main consideration with rune pouches is if you drop yours, you will need to leave yourself enough rift searches so that when you come back, you can get at least the first 4. However, once you obtain the abyssal needle (used to stitch the four rune pouches into a gigantic pouch) if you drop it, you can come back and use a needle on the search rift to get another abyssal needle.

Grab yourself a chisel and weak cell and build as many guardians as you can (keep grabbing another weak cell). They are 110 experience each and you can usually build a few between rounds.