A practical method is presented to generate inflow boundary conditions for the laminar but spatially inhomogeneous flow out of filters, packed beds, or sinter plates. A synthetic velocity field that statistically reproduces the outflow characteristics is created based on digitally filtered random noise by the integral lengthscale of the investigated flow at a low computational cost. The method is tested to reproduce a real flow downstream of a sinter plate, which has its velocity measured using a hot-wire anemometer. Results demonstrate that the present method can efficiently generate synthetic inflow fields.