Aoi Hana, Yagate Kimi ni Naru Recommendations
Both are yuri, and have similar settings; I think Aoi Hana is the better of the two, granted, since while it is also slow boil, the heroines have a pre-existing friendship to build on rather than the suddenness Bloom Into You goes for.
Both series are slow burn romance between females.
Both has more portrayal of the relationship between each protagonists, and how they thought.
Both has more stories about side characters.
These two yuri shows are far from your typical romance anime. Instead of having the main pair fall in love with each other right away, the series focus on the complex relationships between the characters and how their feelings develop. The side characters and their relationships are also an important aspect of the plot, whereas most romance anime predominantly focus on the main cast. If you're looking for a character-driven yuri series with plenty of development, you should definitely give these two a try.
They both approach Shoujo Ai in a mature and somewhat subtle way, all the while avoiding overused tropes and other pitfalls. They both feel very grounded in reality and never stoop so low as to rely on fanservice in order to sell the show.