Working with raster data that causes lateral discontinuity of layers

[AH-CSM]

Hello!
I am wanting to use a raster data set with elevation changes along the model grid but I want to also have a very shallow subsurface layer, about a meter thick, that runs along the top of the model. I want the layer to naturally pinch off as is seen in my problem model area, but attempting to do this with my current knowledge leads to lateral discontinuity within that first layer, which I understand Modflow 6 doesn't allow. I am trying to find solutions to the problem aside from creating a DISV grid since the triangles method won't work in my IDE no matter what I have tried to do to solve the problem of it supposedly being non-existent in my libraries. Is there any way I can have this irregular layer at the surface with my elevation changes without using the DISV or changing to Modflow2005? Any advice would be greatly appreciated! Thank you!