I use ten frames to teach my special education resource students how to subtract with regrouping.
Students start by drawing the ones and tens from the top number in each ten frame. Then they subtract the bottom number. If there is not enough ones to subtract from, then they regroup from the tens by crossing out a ten and drawing an arrow to show a visual to remind them that they have regrouped. Then they add ten ones to the ones side. If they have filled up the ten frame on the ones side (from regrouping), then they add the remaining ones below the tens frame. Then they continue to subtract.