Stone will not be detained immediately. He is still challenging his conviction by claiming juror misconduct, and Jackson is separately still considering his request for a new trial.https://www.cnn.com/2020/02/20/politics/roger-stone-sentencing-hearing/index.html
Trump is already speaking about how unfair the Stone is being treated unfairly:
President Trump on Thursday said he believes his longtime confidant Roger Stone “has a very good chance of exoneration,” but that he intends to let the legal process play out after Stone was sentenced to more than three years in prison earlier in the day.
“I’m following this very closely, and I want to see it play out to its fullest because Roger has a very good chance of exoneration in my opinion,” Trump said during remarks at a prisoner graduation event in Las Vegas.
“I’m not going to do anything in terms of the great powers bestowed upon a president of the United States. I want the process to play out,” Trump added. “I think that’s the best thing to do. Because I’d love to see Roger exonerated, and I’d love to see it happen, because I personally believe he was treated very unfairly.”https://thehill.com/homenews/administration/483912-trump-says-hed-love-to-see-stone-exonerated-but-will-let-process-play