I found my belly breath experience or diaphragm breath in my 2nd year at York University's Theatre department. Everyday we moved our bodies to warm up. Then we would stop and simply lie down. Then close our eyes and breathe. Everyday in movement class we did this. It was an exercise to practice being aware of our bodies in movement and in stillness. For three years in Theatre school, everyday in movement class we practiced this. It is a practice that forever changed by breath experience and it is a practice that I use in my everyday life.
Here's what I have learned: Move your body (any movement - example can be walk or dance or play or yoga), stop in stillness, close your eyes for a moment (about 5 seconds) and then send your breath around your upper belly.
Open your eyes and Invite your breath to move gently in the diaphragm or your upper belly.
Allow and send your mind to the slow movement of your upper belly.
Then slowly invite your breath in your diaphragm or upper belly again, so you can decrease a little bit of holding inside your belly.