Daily Alphabet Book Practice: Read through your paper copy of the alphabet book once a day.  Directions are on the book.

Flashcards: Write letters on cards and tape them up your child will see them (in the hall, on the ceiling above their bed, on the wall by their bed, on the bathroom mirror, by the bathtub, on the refrigerator, in the car on the seat in front of them so they look at it while you drive).  Especially focus on any letters that are tricky for them. Take a few seconds to name them a few times per day and they'll learn them QUICKLY!

Sensory Writing: Get out a pan, dish, or cookie sheet and cover it with something fun like pudding, salt, shaving cream, sand, etc. and have children "write" the letters in it.  

Get Leap Frog Fridge Phonics Magnets.  You may be able to find it cheap at a gently used toy store like Once Upon a Child or you could get it new HERE.

Watch Leap Frog Letter Factory.  This video is how my personal kids learned their letters & sounds- it really works!  Your local library probably has many copies.  You can also stream it on Netflix or Amazon Prime.