Writing on a vertical surface is great for your little one, but why?
When writing ✍ on a vertical surface, the wrist is encouraged to extend, leading to a more mature grasp pattern, and improving the control and dexterity while writing/drawing. This position also promotes stability and strengthening to the shoulder and elbow, encourages bilateral coordination of both hands (when using paper or tracing), promotes crossing of midline (middle of the body), challenges visual attention and hand-eye coordination, helps increase body awareness and posture, and even provides proprioceptive input for children who struggle to stay seated during writing, who may need additional sensory input during seated tasks which they can meet while standing.
In the example below, Eloise tries window crayons. I love these for multiple reasons, kids are fascinated whenever they are allowed to draw/color on a surface that isn't typical (which these allow for use on any glass surface), and I like using many different modalities with art to make it a multisensory experience!
Try these, window markers, or hang large paper and use pencils, crayon, colored pencil, paint, etc. Play at the fridge with magnets, or use an easel or felt board with animals! Most importantly, have fun!