Instead of adding, try taking away.
When a child can't read the clock, the adult instinct is to add: show the minute ticks, draw in a guide line, pile on more of the stuff that explains. For some children that works. For others, every addition deepens the fog.
When it isn't working, try the other direction. Keep only 1 through 12 inside the dial and switch the outer minute numbers off. Leave just the colored circles, and let your child read roughly where the hand is sitting. Take information away, and some children can suddenly take the whole clock in at a glance.
Futatoki the Learning Clock App has a stripped-down setting for exactly this: "circles × simple." One button moves you between adding and subtracting. Try both directions and see which one your child notices in.