Cornick began his youth career at both Bournemouth and Yeovil Town before signing his first professional contract with the latter in 2013. He made his professional debut for Yeovil Town in 2013 and went on loan to various clubs such as Christchurch, Havant & Waterlooville, and Leyton Orient. He rejoined Bournemouth in 2014 but was eventually loaned out to Leyton Orient again, as well as Yeovil Town and Gillingham.