Sorry if you’ve heard this before, but getting the pan hot is important. If the egg is cooked before it gets into the texture, it won’t stick at all. It’s tempting to add the eggs early because cast iron takes so long to heat up, but a cool pan will stick a lot more. I usually let the butter brown heavily before I crack the eggs. If you think that leaves the top undercooked, add a spoon of water and cover the pan to steam the egg tops.

The other guy is right about letting the pan get hot first, but also remember that “hot” doesn’t mean on high, eggs like to be cooked low and slow. Just make sure that it’s actually up to that temp before you crack them in. Flick some water into the pan, if it sizzles for a second or two than that’s good enough for eggs imo (some will recommend waiting until the water drops hover, I feel like that’s too hot for eggs, but you know try both see what you like). I personally try to crack the eggs into the pan before the butter browns, but that’s just me. Another thing to be aware of that’s been mentioned in other threads under this post is that cast iron with a course surface can make things harder, so consider getting a smoother one or sanding yours down. Finally, for your best chance of getting under the egg cleanly, I recommend a thin metal spatula with some flex, like a fish spatula. In my experience plastic spatulas are culinary bulldozers. Be patient, if you think it’s close to done use the spatula to peak under the edge for a bit of a crust to separate from the pan, and if it’s ready, work around the edges to get it loose before you try to move or flip it.

Mine has the opposite problem. Eggs slide around, no stick. However when I crack them on, they spread like water. I recently used Teflon for the first time in years, and the eggs pooled up at a perfect size and shape for a sandwich. I’m jealous. It’s probably a heat thing but the eggs already brown a lot so I didn’t want to make the cast iron hotter