The punishment can be read out loud at the next formation. The punishment can be posted to the unit bulletin board. The Soldier can request an open hearing which could potentially be in front of a formation if you wanted to push the definition. However I don’t believe it is appropriate. In addition to have a public hearing the Soldier must request a public hearing.
So based on the information you provided I do not see an Article 15 proceeding being conducted in front of a formation. I would see this as inappropriate and potentially illegal. I view it as vindictive and belittling to the Soldier.