Ah, I see.
You are correct in that Roth conversions create ordinary taxable income.
I retired two years ago at the age of 46 and am utilizing a Roth conversion ladder.
The way I did it was to save a bunch first in 401(k)'s and IRA's.
I then started saving in a taxable account as my income and savings rate grew.
I reasonably quickly saved up 5 years worth of expenses in a combination of taxable accounts and Roth IRA contribution amounts.
Then I retired and started my Roth conversion ladder.
In general, each year I Roth convert what I expect my expenses to be 5 years down the road. I then spend one year's expenses from my 5 years of after-tax savings.
After five years, I'll have my Roth pipeline full and can continue on that indefinitely.
Doing it this way does require saving up that 5 year taxable nut before retiring.
On the other hand, it also means that those Roth conversions are done at a time when one's taxable income is quite low, so the taxes on the Roth conversions are negligible.
As a real world example, last year I Roth converted a modest five-figure sum and paid federal taxes of $0 and state taxes of $10. In fact, after a few refundable credits, I received a small four-figure sum back from the federal and state taxing authorities, so I actually had a negative tax rate on my Roth conversion last year.
I expect that situation to continue over the next several years. In fact, my biggest tax problem is realizing enough income to take advantage of all of the nonrefundable credits I'll be entitled to over the next several years as my kids go through college.
...
As an aside, I've been interested in early retirement since the late 1990s, and until a few years ago I was planning on doing the 72(t) route. I recently learned about the Roth conversion ladder and for my situation I like it better. A previous poster mentioned the lack of flexibility with 72(t), which is a relatively big drawback for retirees around 50 years old, because you'll have to stay with the program for almost 20 years. Yes, there are ways around this, but they require extra steps and complexity I'd rather avoid. With the Roth conversion ladder, one can vary the conversion amounts annually as needed. But again, I think the biggest trick to the Roth ladder is getting that initial 5 year nut saved up so you can prime the ladder when you're retired.