First I flipped my shirt over and decided where to put the keyhole. I placed a mixing bowl 1" below the top of the shirt and traced the top half. Moving it down a few inches, I trace the bottom half of the bowl. I drew dashed lines to connect the halves, making an oval keyhole. After cutting the keyhole, I cut the 1" strip right in the middle so my shirt was now open at the neck.
Using leftover jersey scraps, I sewed 1 1/2" strips together on the short sides to make about 4' of bias tape (light pink trim). Mine varies from the original in that I used the bias to go all the way around the keyhole since I had raw edges. I folded the tape in half and pressed it to clearly show the halfway line. Pinning the right side of the jersey to the wrong side of the tee gave the bias tape something to hold onto. I sewed the neck and finished the trim before beginning the keyhole, and I left the last 1" on both strips unsewn so I could finish it later.
This picture jumps ahead since I completed the neck trim first, but it shows the bias tape pinned around the keyhole. I sewed the first line of stitches with the fabric on the edge of the presser foot, but I would guess it was between 1/4" and 3/8".
Once the jersey was attached to the back, I turned the shirt right side out and folded the tape onto the front of the tee. I tucked the edge under and pinned it in place, as well as pressed it so I could see if the amount of light pink showing was even all the way around. Sewing on the front of the tee, I tried my hardest to sew almost to the bottom edge of the trim. This was the trickiest for me because I can sometimes get wayward with my stitches.
Here is the neck complete. Next, I pinned, stitched, flipped, and sewed the keyhole following the same steps above. I also used two 3" strips of jersey to make the ties. Folding the right sides together, I stitched one short side and one long side together and turned them right side out.
By leaving 1" unsewn on both the neck and the keyhole, I could fold the keyhole trim under the neck trim and slide the tie in place before stitching.
And voila! The finished product. For $9, it comes super close to the Lululemon version. I even wore it last night to go walking!!