I'm a speech therapist in the schools and here's what I'd like to offer:
Preschool age is a common time for stuttering to occur. This isn't to say all preschool stuttering is typical and will be outgrown. I'm not sure if there is a reason you are seeking alternatives to speech therapy. A speech therapist is who the pediatrician will refer to for these kinds of concerns. This service is provided free through the school systems if a child qualifies. Even if he weren't to qualify the speech therapist can provide specific techniques based on the child. I would recommending having the parent contact the school district early childhood special education services and they can direct them from there as far as the procedure goes.
In general, tips are for the parent/provider to:
Model a slower speaking rate. When you speak to the child, you speak slower. Use more pausing. When you ask the child a question, wait for their response. When they ask you questions pause a second or two before responding so they can learn to do this. These are just a few general ideas. I'd really recommending following up with the pediatrician and/or contacting the local school district. Services are provided from birth on up. Good luck.