Sometimes the Montessori approach for reading does not work as expected. There are some children who are not able to read phonetic words very well after they have been presented the Montessori method of sounding out letters, spelling words and reading words. This even happened to a Montessori teacher's child!
What do you do if your child is not a phonological reader? You have to teach words! One of my children could not figure out how phonetic words and the exception to the rules worked until he memorized words. This method takes time and your child's reading skills may take longer, but it worked for us. My child was able to put together the Montessori elements of reading after memorizing words. His reading skills suddenly soared when he was ten years old.
I know that Montessori teachers don't believe in using flash cards of high frequency words, but it might be something to consider. Children like learning new words, just make it a fun, non competitive game. Let your child pick out what words he or she would like to learn.
Use any printout of pictures with labels as matching exercises. For a more challenging game use words without a picture prompt.
Make 2 to 4 sets of each matching word on note cards and play a modified game of "Go Fish".
Also, there are free interactive reading games online.
Use words your child knows to write stories that are fun to read.
Montessori 3 part cards with the picture and word on one card are perfect for matching games. The most important element to consider is what your children find interesting to read. Cater to their interests and they will have instant motivation.