Is your room neat and tidy, with very few knickknacks on your dresser and desk? Then you can describe it as uncluttered.
Uncluttered places are clean and spare, without too many objects filling the space. The design of a building can be uncluttered, lacking fancy decorative details, and your friend's uncluttered jewelry design is likewise sleek and plain. An uncluttered room specifically lacks clutter, disarray or collections of things strewn around. And if your mind is uncluttered, it's free of unwanted emotions and thoughts.