The phrase "be formed of" refers to the process of creating something from different parts or elements. If you're looking for alternative words to use, consider using "comprised of," "composed of," "made up of," "consisting of," or "constructed of." These synonyms can help vary your sentence structures and add nuance to your writing. Additionally, if you want to emphasize a certain aspect of the composition, you can use more specific phrases such as "assembled from," "crafted from," "fashioned from," or "forged from." Mixing up your language can also help prevent repetition and make your writing more engaging for readers.