Rhyme Phonics is the easiest and simplest phonics activity book series.
Book1: Single Consonants
Book2: Short & Long Vowels (cvc+e)
Book3: Consonant Blends
Book4: Vowel Blends (Long Vowels & Diphthongs)
Each lesson teaches the sounds with only four letters, it gives them patterns(rhyming words, word families) to repeat.
No extra various activities, so that children can only, simply concentrate on the sound and letter connections.