Keep doing timed tests. Although it’s not the most enjoyable thing for the kids, it definitely helps build automaticity. Some things just have to be memorized!
We also love addition war and ADDIT (my late addition bingo game naans
). Flash cards with a friend is always on the early finisher and free time list. We’ve done math bees, math jeopardy, math board races, etc. I think any way you can practice is going to be beneficial.