Piper has learned about 50-60 sight words so far in the last month. We add a new one about every day, sometimes more than one. She picks them up faster if it's one that she requests or has been seeing a lot in her books. So far it's just memorization, which is pretty much the same way I started reading. It's funny that she knows her letter sounds, but isn't at the point where blending them together works for her.
Here are a couple videos showing her making dictated sentences for me. Usually we mix them up and she makes them a couple times again. The second video has a long sentence for her and she had a hard time getting started. It was chaotic as well with Stella "helping" and I edited out the first half of the video.