Katie_Deely started a post on the ESO sub-Reddit that discussed her favourite delve for provisioning mats. A few others mentioned their favourite locations as well.
Some of the recommended places were
- Faldar’s Tooth, Reaper’s March, Aldmeri Dominion
- Sanguine’s Demise, Shadowfen, Ebonheart Pact
- Vile Manse, Reaper’s March, Aldmeri Dominion
- Hallow City, Coldharbour