This strategy is often the first taught to students.
In the first grade room I am working in, many students come up to me asking for help with spelling. I will ask them to sound the word out, and they can spell it most of the time because they are hearing the sounds.
Once students have learned to sound a word out, they start to learn to spell words with combined letter sounds, such as about, church, judge, and others.
Along with this, they learn the rule that goes with each letter combination.
I worked with a first grader who was starting to read. I noticed that she came to words like "about," and tried to sound it out but couldn't quite get it. I wrote the word down, along with some other similar ones, and explained the "ou" rule to her. It took some time, but it clicked!
To help students with visual spelling memory, you could use a word bank on a worksheet. The bank could have words focused on one rule, like combining "ou."
A 7th grader I teach piano to was at her lesson one night. She spelled out a music vocabulary word and said, "This doesn't look right." I helped her a little bit, and she was able to come up with the correct spelling.
The first grader I mentioned earlier was writing something down one time I was with her. She sounded out the base word, which she spelled correctly, and then realized that she could just add the "-ing" ending to it to get the correct form. I think this type of instruction helps students to associate things while spelling.