How Do I Make The Whole Bottom Layer Covered In Solder Mask

[finalman]

I'm designing afew simple circuit boards with only a few pads, traces and vias on the top layer and a few vias and traces on the bottom layer.

Now for some reason Diptrace is not creating the bottom solder mask layer.

If I put an un-needed single small isolated pad on the bottom layer the issue gets resolved but I want to eventually sell my PCBs but won't do that yet because doing that fix makes my work look unprofessional.

How in Diptrace do I make the whole bottom layer covered in solder mask?

[Alex]

The whole bottom layer will be covered if the bottom mask layer is empty. In other words, solder mask layers define areas where board is uncovered.
If bottom mask layer is empty you can exclude it at all from Gerber files to avoid confusion on manufacturer's side.

[finalman]

I would've expected because there are vias and traces on the bottom of the PCB those would be covered by default to stop shorting and copper corrosion but I guess it doesn't work that way.

Even if I specify the vias to be "tented" in the "Mask / Paste settings..." nothing changes.

Instead Diptrace appears to only create data for that layer when a pad is added.

EDIT: The 3d viewer also clearly shows the vias covered with solder mask.