This letter aims to develop an innovative, fast, and effective technique to design radial line slot antennas (RLSAs) capable of obtaining nonconventional radiation properties by means of combining analytic approaches with optimization techniques. This technique allows to obtain much more complicated designs than the classical ones, including maximum directivity/gain and sidelobe level (SLL) control as examples of classical designs, in a quite faster way, but has a disadvantage that a proper error function for the optimization procedure which captures all the design requirements must be found. To verify the validity of this design technique, we compare it with other design techniques, and we have particularized it to the design of antennas with highest gain.