In addition to their Words Their Way spelling list, I give my students three "red words" a week. They are called "red words" because students often stop when coming across these words in their reading. They are words that cannot be sounded out and therefore need to be memorized.
Here's a set of flashcards taken from Stages 2&3 of Orton-Gillingham "red words". Suitable for second graders to practice the "arm tap" (Hold strip in one hand and use other hand to tap out the letters in the word).
Keyword: Orton-Gillingham red words