ADS Momentum problem with the layers

I want to define and map the layers in order to simulate a microstrip transmission line with a gap with a dice of dielectric that is placed over a gap and touching microstrip line on both sides. I am not sure how to map the layers and whether it is possible to have a dielectric as layer 1, as I tried to map (strip) the layer and it creates another cond layer (cond2) on the top of the piece of dielectric.

So the layout is:

Free space
piece of dielectric placed over a gap (diel2)
microstrip line with the gap (cond and mapped as strip, on the top of dielectric)
Ground

I would appreciate your help.

Thank you in advance,
Derek