We propose a phenomenological model designed to study electron spin relaxation in large quantum dots. The versatility of the model lies in its ability to incorporate both Rashba and Dresselhaus spin-orbit interactions with variable relative strengths and realistic confining potentials with only a marginal increase in computational complexity and time. Good agreement has been found with results from path-integral simulations of spin relaxation by Chang et al. (Phys. Rev. B, 70:245309, 2004).