Slice in surface view created from extracted surface not working

I have a tubular geometry with fluid flow and velocity data in every point of my computational domain. I would like to get a slice at a desired cross section only with the fluid cells (like in the picture but without the blue border where isnt any flud)

Because the velocity field contains wall cells, too (the domain is divided into cubes) I first do the Find data filtering by non zero velocity and then on the extracted surface I use the slice. But in the surface mode I get just points and no surface interpolation which looks not very nice.
Is there any way how to do that? I hope that it is clear what I am thinking of…