'sloppily-installed' is a modern compound formed from the adverb 'sloppily' + the past participle 'installed' in Contemporary English.

'sloppily' comes from 'sloppy' + suffix '-ly'; 'sloppy' (mid 19th c.) developed from 'slop' (noun/verb) meaning a messy, liquid substance or to spill. 'Installed' comes from Medieval/Modern English use of the verb 'install', ultimately from Medieval Latin/Italian/French forms of Latin 'installare' (in- + 'stallare'/'stallum') meaning to place or set in a stall or position.

Originally 'sloppy' was associated with 'slop' (messy liquid) and then extended to mean 'messy or careless'; 'install' originally meant placing someone or something in a stall/position and later broadened to mean setting up equipment, furniture, or software. The compound simply combines these senses into 'placed/set up in a careless way.'