Okay, so I'm kinda obsessed with this pairing, and I've been through a lot of fics hunting for that perfect, excruciatingly slow build. Honestly, the tag can be a bit misleading sometimes; people slap 'slow burn' on anything that isn't immediate smut. The one that really stands out for me is 'Conductivity' over on AO3. It's set in a university AU where Edd's an engineering student and Tord's in fine arts, and the author has this incredible patience with their dynamic. They're neighbors who share a wall, and the progression from annoyed acquaintances to tentative friends to something more is measured in months of in-story time, full of miscommunication and little breakthroughs.
What I liked is that the tension doesn't just come from 'will they/won't they' but from their fundamentally different worldviews clashing. It's less about dramatic confessions and more about learning to speak each other's language. The author updates sporadically, but each chapter feels worth the wait. There's another one, 'Red Strings and Schematic Things,' that has a soulmate premise but twists it—Edd can see mechanical faults in objects as red strings, and Tord's art is somehow intertwined with that. The romance is a very slow subplot to a bigger mystery, which might frustrate some, but I found the payoff massive when it finally shifted focus.