This is the 17759th most frequent Polish word.
zrobiona
"Zrobiona" means "done" or "made" in English.
Here the word 'zrobiona' is used as a past participle modifying the noun 'praca' (work), indicating it is completed.
Ta praca została zrobiona przez Zofię.
This work was done by Zofia.
The word 'zrobionej' is used in the genitive case due to the noun 'prezentacji' (presentation) which it modifies.
Jestem bardzo zadowolony z dobrze zrobionej prezentacji.
I am very satisfied with the well-done presentation.
In this context, 'zrobiony' is used as a predicate adjective referring back to the subject 'fotel' (armchair), describing its material.