A depth of field that extends 10cm to infinity would suggest a lens focused at no less than 20cm.
Assuming the lens is fixed focus then approximately 20cm should be ideal. If the lens has variable focus, then optimal distance would be the minimum focus distance, or where the subject fits w/in the field of view.
The caveat is that we don't know what standard was applied to determine the camera's depth of field... the ideal distance in any case will be the shortest distance that is also maximally sharp.