This is a complex process so let's get started: you find yourself having sewn welting all the way around a cushion and now you need to make the two ends meet. How can you do this and make it look good? Won't it look lumpy? Science has a cure! ;D
As you can see when you start this process, the cords overlap, which is by design: we wouldn't have room to do the following overlapping procedure unless we had some excess fabric over the cord to overlap.
Now it's time to take out the stitching in both ends using a seam ripper most likely.
Peel apart the layers of the welting:
In my case I had more than one row of stitching to undo because I like to pre-finish all my edges using the serger to prevent shedding and fraying--velvet is a very fray-prone fabric.
Choose now which side will have a longer fabric end than the other side: this side will be folded over the shorter-fabric-end-side.
On this longer side, prepare the cord by gently pulling it up & out of the fabric, but don't forcefully pull it out of the welting tube.
This is the longer fabric end side after trimming the cord:
The next photo is an optional step: serge finish both ends of the fabric tails.
You will have to fold the longer fabric end under so that it still covers the cord well.
Here comes the tricky part: matching up the ends.
Hold the cords as shown to measure where to cut the longer end of the cord. You will have to carefully ensure that the way the cords meet allows for no slack to avoid making a bump in the welting. Basically both sides as they overlap must be completely flat with the cushion fabric.
Time to cut the longer side of the cord so it creates no bump in the welting and reaches the other side perfectly. You can experiment by holding it closed with your fingers to check the length. In fact, if you're worried about the cords moving too much and ending up showing a gap on the outside you can even sew the cords themselves together by hand.
Now assemble the two sides so they can be basted together. You can use pins if needed.
Now baste through all layers along the lip, right under the cord to secure it for sewing.
Voila!
Whew! That was a lot of work but my furniture benefitted a lot from it. According to my calculations, for this project I had to complete the above procedure 18 times!
Love,
--Pam