The word "ancient" has never appeared in Oracle Bone Inscriptions (because Oracle Bone Inscriptions was used for divination in Shang Dynasty, many descendants' words were never used in it, and some words were not used at that time). At present, there are usually two ways to deal with the problem of missing characters in calligraphy: one is to create characters by yourself, such as "Gu", which can be used because both parts are found in Oracle Bone Inscriptions. The second is to use common characters, which can be replaced by the word "employment" with the same pronunciation as "ancient". The word "employment" has existed in Oracle Bone Inscriptions.
So if you want to write the word "ancient", you can use these two methods (see figure).