Between the posterior edge of this process and the anterior surface of the ethmoid bulla, there is a two-dimensional space, resembling a crescent shape.

This concept is easier to understand if one imagine the infundibulum as a prism so that its medial face is the hiatus semilunaris.

The uncinate process can be attached to either the lateral nasal wall, on the lamina papyracea (50%), the anterior cranial fossa, on the ethmoidal roof (25%), or the middle concha (25%).

This article incorporates text in the public domain from page 155 of the 20th edition of Gray's Anatomy (1918) G., Arun et alli (2017) - Anatomical variations in superior attachment of uncinate process and localization of frontal sinus outflow tract.

International Journal of Otorhinolaryngology and Head and Neck Surgery, 3(2):176-179 P.S., Hechl et alli (1997) - The hiatus semilunaris and infundibulum.