FDR tried to do it in the 30s as part of his ‘new deal’ - the Constitution doesn’t specify the max number of SCOTUS judges. So, if you want to pack court in your favor, add seats and have your senate cronies confirm (that’s why it has to be ‘trifecta’ - wh, senate, & house must all be held and align with the ruling party’s dictates). Fortunately for us, many of FDRs ‘friends’ in congress told him to pound sand.