I have had a lot of stomas to close since they have moved mine 4xs.
All have closed on their own in their own sweet time...nothing that I do or do not do will change that. I just keep them clean and covered with sterile gauze, protect them and the skin around them with something and avoid bathing for the first while, No swimming pool until they are completely healed or granulated in.
To avoid ugly scars at I do pull the edges closer together with steri-strips but I do not try to close them completely.
Sharon