Bottom layer exposure for prints placed directly on the bed (resin printer)?

Question

I have an Elegoo Saturn Mono resin printer.

If I make a 3D model that has a "sacrificial layer" on the bottom, and I place it flat on the bed, will the area in contact with e bed automatically be exposed as a bottom layer with a longer exposure time, or is this something that I will need to do manually?

I'm using Chitubox and an Elegoo Saturn for the printing, and Blender to make the models. I have them all set to the vanilla settings\factory defaults, and am not using any customer setting.

My thinking is that if I have a large object to print that is going to have a flat base, such as a slab of rock for scenery, rather than using lots of heavy supports I could simply add extra material on the bottom of the object, a couple of mm thick, and then sand the entire thing flat using a belt sander and high grit paper to get back down to the material that I actually want.

Answer 1

If you put the object directly on the bed, the lowest part of the object will be cured as the bottom layer. And yes, you can sand it away depending on the shape of the object.

For such large objects, you can also use a feature called Double Exposure, it is available on few slicers and easier to deal with.