Liverpool started brightly at the Hong Kong Stadium after witnessing Leicester beat West Bromwich Albion on penalties in the tournament opener.
The first goal came on 60 minutes, summer signing Solanke thumping past Wayne Hennessey from 22 yards.
It was set up by an audacious flick from Origi, who ensured victory with 10 minutes to play after Philippe Coutinho's shot had deflected into his path.
The final kicks off at 1.30pm BST on Saturday. Crystal Palace meet West Brom in the third-place play-off at 11am BST.