Flavin prenyltransferase that catalyzes the synthesis of the prenylated FMN cofactor (prenyl-FMN) for phenolic acid decarboxylase C. Involved in the decarboxylation and detoxification of phenolic derivatives under both aerobic and anaerobic conditions. dimethylallyl phosphate + FMNH2 = phosphate + prenyl-FMNH2 Homododecamer. Belongs to the UbiX/PAD1 family. YclB subfamily.