Here is an approach for introducing Aa to Zz letters linked to sounds with the three core phonics skills and their sub-skills for pre-schoolers 3+. I provide my rationale and a PowerPoint for transparent review about these two cumulative books:
https://phonicsintervention.org/nursery-books/
Launch March 2017: Debbie's Phonics and Talk Time bks 3+
Launch March 2017: Debbie's Phonics and Talk Time bks 3+
Debbie Hepplewhite