When ओ joins a consonant it is written as the sign ो: क + ो = को.
को खो गो पो मो रो सो
Every word here uses only this matra, so children can read it as soon as they know the letters and this one sign.
See every consonant with every matra in the barakhadi chart, for example क की बारहखड़ी.
Play the varnamala gameTap the letters in order before the clock runs out.