I was talking about the layer infos in the landscape editor, not anything inside the material. When you create the layer info for each of your layers, you can choose from weight-blended or non-weight-blended. Weight-blended layer infos are normalized against each other, so will total to 100%, non-weight-blended layer infos are all independent and ignore each other.
People often run into trouble if they use the older “Landscape Layer Weight” nodes in the material (which have a “base” input which isn’t itself a layer) with blended layer-infos instead of the newer “Landscape Layer Blend” node. If you’re using the latter, you are probably already set up right and just need to paint your whole landscape with your chosen base layer before you start painting anything else (the component brush is good for ).
We need to do some work on the landscape create process so that a “base” blended layer can be designated which will be auto-filled across the whole landscape, I think.