The paper pioneers the identification of a successive number of distortions of shape and cut of tetragonal domains in a magnetic field perpendicular to the plane of a ferrite-garnet (1 1 1) slab. Theoretical research has been conducted into the dependence of the structure and orientation of a flat domain wall (DW) in the (1 1 1) slab upon material quality factor Q and ratio κ1 of the cubic crystallographic and induced uniaxial anisotropy constants. A qualitative description of the changes of shape and orientation of tetragonal domains from rectangular to rhombic is presented.