"don't do it". Probably not the answer you were looking for, but disposables are never going to perform well when side sleeping. If you need to wet while laying on your side, cloth is your best option. You can try to bulk up with disposable and will get some improvements if you tweak how you do it, but it'll never be reliable. Point down, make sure there's a good pocket in the front, get a diaper with thick padding that has good wicking but also sap, insist on good leak guards, fasten your tapes tight, attach the lower ones to seal around your leg not around your waist. If you don't wet a lot, that might be enough, but you'll probably still leak occasionally.
If you're wetting while asleep, you may just need to adjust to laying on your back. If you're waking to wet, roll over on your back, wet, wait a bit, then return to your side to get back to sleep. (that's what I do)