Schematic description of our lens simulation procedure. To produce each simulated stamp, we started with a potential deflector and a target Einstein radius, θ_E. Then, we picked a set of parameters for a mass model consistent with the target θ_E and the deflector’s light, and we performed a check where we made sure that log M, f_*, and Υ are within physical ranges. After that, we picked a source using the target z_s provided by the mass model parameters, and we placed it randomly around the caustics before simulating its lensing by the mass model. Next, we convolved the lensed source image with the deflector’s PSF, downsampled to match the pixel size of CFIS, and added Poissonian noise. At this point, we added the original stamp of the deflector to get the final mock. Lastly, we performed a contrast check to make sure that the lensing features are visible. If it passed the check, we accepted the mock and proceeded to the next deflector. Otherwise, we repositioned the source relative to the caustics and tried a second time.