Question about creating an oatmeal layer

[MaRanda]

I want to create a bar with an oatmeal layer on one side. Logic tells me that I could simply line the bottom of the mold with a layer of oatmeal and then pour the soap in, but I know that some people mix the oatmeal at trace with a small batch, pour that first, wait for it to harden a bit, then pour in the rest of the batch, sometimes using different oils for this exfoliating layer. Since I tend to purchase soap with a layer of oatmeal on one side, I'm inspired to do this myself. What works better?