Here’s a tip: when you have a window in the bathroom, use slab, or solid pieces of stone for the window surrounds. This takes away the issue of repainting wood trim, mold on the wood, or wood rot. Plus it just looks good!
The slab on the threshold should be pitched.
Local granite and marble suppliers can cut you remnants that are 3/4″ thick.
(Click on the image for a larger view.)