"Can I submit manuscripts to Flapjack Press and are there any job vacancies?"
Flapjack Press is currently closed to unsolicited manuscripts as it has a full publishing schedule.
Anything speculatively submitted will not receive a reply.
And there are no job vacancies either.
However, Flapjack IS now open to submissions for its forthcoming anthology, NeurodiVERSE.
Guidelines can be found at NeurodiVERSE - Call for Submissions.