Plenty of flexible steel shafts from L-flex, A-flex (as senior flex is sometimes called) and so on.
Should also consider shaft weight, some superlight steel shafts available now, down into the 50g range, much easier to get back to the ball. Weight may be more important than flex.
Stepping normally relates to taper tip shafts. There are specific length blanks for each iron. Shafts get progressively stiffer as they get shorter and the tip section (distance to the first step) gets shorter. If you are "between flexes" then you can soft step by putting the 3 iron shaft into the 4 iron and trimming more off the butt to get the right length, carrying that process down through the set. you can normally do this 2 or 3 times, the 4th soft step would take you into the next flex down so there is no point. Conversely you can hard step by putting a 5 iron shaft into a 4 iron and butt trimming less to get the right length. The fun starts if you want top hard step & do over length clubs as you may have to add length to the shaft to get the required length.
The thing about doing it with parallel shafts is that all shafts are the same raw length and the same distance from the tip to first taper when they are uncut. You would normally cut a different length of the tip (club to club has a half an inch difference) to produce the desired shaft. I have had in the past a set of True Temper shafts that were specifically designed to be a variable flex and tip trimmed for the desired flex.