Here are plans for two dories, Little Sister and Big Sister.
The Little Sister design is basically just like any 18′ x 4′ (5.5 m x 1.2 m) banks type dory. The Big Sister design is a 19’5″ x 5’6″ (5.9 m x 1.6 m) banks type dory.
The plans are well thought out and explained. The build should not be very difficult for a first-time builder.