The senior creative team of Phil Evans and Guy Vickerstaff are the founding partners alongside Caroline Garrad, an account director at the agency.
Toast, which will be privately funded by the partners, opened its doors this week but has yet to take on any clients.
It is positioning itself as an agency offering greater direct contact between creatives and clients, and a heavier emphasis on team thinking, in a bid to offer a fresh alternative to traditional ad agencies.
The founders have yet to decide upon a media partner.
Garrad will be responsible for client services at Toast. She has formerly worked at Faulds Advertising and 1576 on accounts including Direct Line and Miller Homes.
Evans said: "It's been in the pipeline for a while. If we can survive in the current climate then we can move on from that."