To make a new layer from several other layers (one flat layer, not a smart object)...
Hide any layers you don't want in the new layer
Select the topmost layer in the layers palette
Use keyboard shortcut Shift/Option/Command/E (Shift/Ctrl/Alt/E on pc, I think)
This will create a new layer containing only the visible layers in the document.
One thing to remember, this layer will be the new topmost layer (covering all the others) and if you try to edit the other layers, you will pull your hair out trying to understand why none of your changes are working unless you remember to
hide this new layer!
I use this all the time. Works great for me!