Twitter is to thank for the two coming together on the project. Last summer, Saxe tweeted at Morris saying that he was a fan of her. The two of them exchanged some tweets, but it wasn't until Saxe and Julia Michaels made a trip to Nashville for some songwriting sessions that the song actually came together. All of those participating in the writes were tested for coronavirus beforehand and then quarantined together for around 2 weeks. During that time, Morris and Saxe wrote together a few times where "Line By Line" was created.
Morris credits the song coming together due to both of them finding the same things within song lyrics because of their individual relationships. Both Morris and Saxe are in relationships with other artists, Morris with Ryan Hurd and Saxe with Michaels. She immediately played the song for Hurd because she wrote it with him in mind.
The collaboration is just the first of many projects Morris is sharing this year. She has "a lot of stuff in the pipeline for the spring." Plus she is working on her next solo project, but confessed she's still writing. Because of her tour getting canceled again due the pandemic, she's hoping that she can use all of her free time to finish her next record sometime this year.