How do I print with infil open on the top and bottom

[eviL1776 0]

I am trying to make a mold for a wax part, I want to have a print that is open on the top and bottom for cooling but I want the floor of the cavity to be solid.

I can have the bottom open by setting the bottom thickness to 0 but if I set the to to 0 the cavity ends up with a open base. I have pictures of what I want but don't know how to add them to this. i have seen this done on other printer software by setting it to not print the top 10 layers. Is that possible with Ultimaker Cura? Note: I have a Ultimaker S5

the first 2 images were printed by someone else the last is what happens in cura leaving the top and bottom set to 0

[AndersK 29]

You could model the bottom of the cavity as a separate part and use Per Model Settings in Cura to specify top and bottom thickness larger than zero.