You can try searching on some popular fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfics, and you can use the search filters to specifically look for Attack on Titan Yuri fanfics.
Another place could be FanFiction.net. However, the tagging system might not be as precise as AO3. But still, if you dig a bit and use relevant keywords in the search bar, you might be able to find some great Attack on Titan Yuri fanfics. Also, you can check out some Attack on Titan - related forums where fans might share their favorite Yuri fanfics.
There are also some Tumblr blogs dedicated to Attack on Titan fanfiction. Some of these blogs might focus on Yuri pairings. You can search for relevant tags like #AttackOnTitan #YuriFanfic. But be aware that the content on Tumblr can be a bit unorganized compared to the dedicated fanfic websites.
If you want the clearest chapter reference, go to Chapter 186. Early on, Seeing Wen Jiaojiao bravely entering the pigsty, Jiang Yan couldn't stay...; later, the chapter leans on He accepted being left behind by Jiang Li..
A practical answer is Chapter 159, because it turns the idea into a concrete scene. The chapter opens with Seeing the red light of the camera turn on, Su Yinwan looked at the..., adds pressure through The moment the door closed, he straightened his back, and his originally..., and ends on Shang.
If you want the clearest chapter reference, go to Chapter 188. Early on, With a "snap," the pencil Jiang Cheng was using to draw broke on the paper.; later, the chapter leans on He looked up, the cold glint behind his glasses sending shivers down one's....
The best chapter pointer here is Chapter 203, "She's Not Her Maid!". It opens with Ah Fu knew he might have made a mistake, and after glancing at Su Yinwan,... and closes on Su Yinwan's expression stiffened for a moment but then quickly returned to....
The best chapter pointer here is Chapter 181, "Are All the Weibo Followers Police?". It opens with Xiang Hao rushed to the police station as soon as he saw the trending... and closes on Let's not be too hard on a young girl.] However, these defiant words only....
If you want the clearest chapter reference, go to Chapter 178. Early on, Wen Jiaojiao is just too unreasonable, why does she have to single out...; later, the chapter leans on She's just new here, isn't she?" "Exactly, Wanwan is obviously doing it by....
Chapter 179 is the strongest chapter-level answer because it starts from Everyone originally had no expectations for the gifts that Su Yinwan... and follows through on I've been craving one for a long time!" Fans: ?.
The best chapter pointer here is Chapter 160, "The Mushroom-Picking Party of Six". It opens with As the sky gradually darkened, the originally mild drizzle began to... and closes on Then came Shu Yan and Jiang Li, while He Yun silently moved to the back of....
The best chapter pointer here is Chapter 217, "No Problem, They're All Red Anyway". It opens with But Director Sun didn't plan to give her any room to think, he directly... and closes on Although her initial performance was mediocre, fortunately, Jiang Li....
If you want the clearest chapter reference, go to Chapter 221. Early on, Many agricultural students found themselves with tears brimming in their...; later, the chapter leans on Great, the hardships of agricultural students have finally been discovered..