Flat head in Babies is very common mostly on one side initially when the baby is not flipping on the sides in the first few months . so because of the continuous pressure over the soft skull bones such flattening can be there . This will become normal by itself gradually when the skull grow in size and shape with age . No musturd seed pillow or any such kind of intervention like massage is required for the corrrction .

Looks normal . Usually gets to shape as baby grows . Have a check on head circumference during every visit

Nothing to worry about. Looks Perfectly normal.