Base tee: turn wrong side out. Cut off hem; cut open both side seams to underarm.
Cutting and Preparing strips using other tee: lay tee flat; from hem measure 4.5" draw a line across and cut strip. Repeat until you have 4 strips.
Cutting and Preparing strips (cont'd): cut one side of each strip. Which should give you a very, very, very wide piece.
Cutting and Preparing strips (cont'd): finish top and bottom of each strip. Either serging or using pinking sheers. (just the top of your bottom strip, as it is already hemmed).
Cutting and Preparing strips (cont'd): make gather stitches at top of each strip. On your machine, set stitch length to the longest length; sew 1/4" from edge, then repeat stitch 1/4" from first stitch.
Positioning Strips on Base Tee: measure 1" from bottom of base tee and mark. position bottom strip; gather and stitch in place.
Positioning Strips (cont'd): from top of bottom strip, measure approx. 6" and mark. position the next strip; gather and stitch in place.
Positioning Strips (cont'd): repeat step 7 for the rest of the strips.
Finishing: with right sides together, pin side seams including edges of the strips; stitch through all thickness. Hem bottom of tee.