I´d make my phylactery something absolutely common, but at the same time durable, like the adamantine doorknob of the adamantine door near my inner sanctum, or one of the gears in the trap that protects a place near my inner sanctum. The phylactery would receive Nystul´s magic aura spells to nullify it's aura, so it doesn't register as magical.
At the same time I'd have several false phylacteries on places like a hidden demiplane, a dungeon protected by constructs, traps and undead and stable geodes deep underground. I'd research specific spells to defeat divinations that could reveal that those those items are not phylacteries, specially Analyze Dweomer. I'd leave subtle clues, riddles and misinformed minions to reveal the location of those false phylacteries.
Finally, as soon I have the opportunity I'd spend some time deciding how to word a Wish spell with the purpose of foiling any Commune question trying to determine if I've been deeated once and for all to say that efectively, I'm definitely dead and won't reform again.