I was not aware that slippery elm was indicated for gut inflammation. I am familiar with it as a remedy for sore throats/hoarseness and topically to relieve irritation caused by skin allergies. I did just google it and it says it can be used for upset stomact/diarrhea. As for IBD, I am not sure.
If you are looking for something for IBD/inflammation, I have been taking turmeric for the past 1.5 years and I am happy with the results. A naturopath who happened to be on the ward with me when I was first diagnosed with UC, actually recommended turmeric, though I did not start taking it until years later. These days, its not uncommon for GIs to recommend it to their patients. It's good for joint pain as well.