More like wire of the half length (monopole) with good reference. Slot is pretty much equal to a dipole and resonates best at double the wavelenth of its longes

More like wire of the half length (monopole) with good reference. Slot is pretty much equal to a dipole and resonates best at double the wavelenth of its longest axis. This assumes single narrow and straight slots. Quite fancy radiation patterns, polarization and resonance points can be implemented with fractal shapes of slots.