'flawlessly-performed' is a compound formed in Modern English from the adverb 'flawlessly' and the past-participle adjective 'performed'. 'flawlessly' derives from 'flawless' + the adverbial suffix '-ly'; 'performed' derives from the verb 'perform' + the past participle suffix '-ed'.

'flawless' comes from Middle English 'flaw(e)less' built from 'flaw' (of uncertain origin, attested in Middle English) + Old English-derived suffix '-less'; 'perform' entered English via Old French 'parformer' (from Medieval Latin/Latin roots) and became Middle English 'performen', leading to modern 'perform' and its past participle 'performed'.

The components originally carried their literal senses — 'flawless' meaning 'without flaw' and 'perform' meaning 'to carry out' — and in the compound the meaning has remained consistent: 'carried out without flaw'.