So if you go into the slime cave core (where the slime dragons are) and loss to one they coat you in slime. You can then go to the fire in the room and it will give you the Slime Strip which you can take to the wizard and have researched. I just don't know if the cutscene with the blacksmith afterward is all that is supposed to happen.
Viewing post in [RPG] GROVE: "Dark Places" (v0.308) comments
No, there is a separate cutscene that is available after the slime strip is researched. look at this guide https://qazm.itch.io/a-grove-timeline