Numerical simulations of laboratory-scale experiments, with no wind imposed, were performed for fuel bed slopes ranging from 0° to 45°. The implementation of a vertical symmetry plane (SP) placed, span-wise, along the middle of the computational domain, was assessed as an approach to reduce computational cost. The simulations were performed with Wildland-urban interface Fire Dynamics Simulator (WFDS). The experimental trends of the compared quantities were reproduced well by the simulations. Radiative heat transfer is the dominant mechanism of heating for slope angles between 0° and 22°, and convection heat transfer mechanism starts to be relevant and becomes more important than radiation for slopes of 31° and 45°. Similar to other studies, it was found a “critical” angle of ~22°. For slopes angles greater than the critical value, there are significant changes in the wind conditions at the base of the flame which result in a more rapid increase in the rate of spread with increasing slope.