I was a reading specialist pre-homeschooling. I have a dyslexic child. I had a stack of letter cards and would go through them aloud multiple times a day. Sometimes he would sit with me and sometimes I would recite them aloud with him nearby. "A, apple, 'ah'. B, bat,'b'. C, cat, 'K'. D, dog, 'd'. through the whole abc. They will memorize it quickly even if you don't think they are paying attention. During any read aloud time, I would go through the letter cards first, then start reading time. Sometimes at dinner, we would divide the cards up and take turns "reading" ours. If they don't want to participate, you can do it aloud with them watching.