Digging is all I know that really works but someone might know a good trick?
I dug a bunch 2 years ago in a bed that's again been neglected and I see they've made a triumphant return.
Those little bulblets don't take long to establish and start the process all over. It was a hasty fall job and I piled them on my (rural) driveway intending to dispose of them later and found myself preoccupied with more desirable projects. The next spring I had a big, green mound of wild onions to deal with. Luckily they were concentrated on gravel for easy kill and removal.
Oh, the ones you dug? Burn pile or otherwise removed from your property.