Studio Desk with treatment?

[jwl]

It won't cause bass buildup, in fact it won't have much effect on the bass at all. The long wavelengths (bass frequencies) will tend to simply diffract around objects in the room, even relatively large objects like the desk.

The main issue with treatment for a desk is to make sure you know what is happening with the high frequency reflections from the speakers. Most desks are angled to aim those reflections away from your ears.