3D model created from a 2D public domain image. I decided to continue the exposed blue glass on the sides of the fragment too. Dimensions are relatively accurate.
[Glass relief fragment](https://www.metmuseum.org/art/collection/search/249605?searchField=All&sortBy=Relevance&ao=on&showOnly=openAccess&ft=roman+wall+fragment&offset=80&rpp=80&pos=98) via The Metropolitan Museum of Art is licensed under CC0 1.0