How do you put a zip in a cushion?

[UnSerpentQuiCourt]

I thought it would be quite easy; just pin the zip (closed) into the seam where the two parts of the base join and sew in.
Then I made the mistake of checking online just to make sure, and it is so complicasted! I seem to need a sewing machine which does 'basting stitch' and a 'zipper foot' and I can't understand the instructions.
Is it really that hard? (I have not got the above - all I can do with my sewing machine is straight sewing.)

It's not that hard.

There are a number of ways you can do it. Personally, I like piping on all my cushions so it's not practical to have a zip along an edge seam, so I put mine about 3/4 of the way down the back side with a flap of fabric over it so that it is covered.

You do need a zipper foot, ideally, it allows you to get closer to the zip teeth when sewing so you don't have an unsightly zip fabric dge showing.

I sew my zip into my back pannel of fabric before assembling and sewing the cushion.

What I do it have two bits of fabric, in total measureing 2 inches longer than the front panel of fabric. I sew one piece of thsi fabric to one edge of the zip, right sides together, then sew the other edge of the zip to the other piece of fabric, right sides together. Then I press and topstitch. Then I fold over the fabric from the top panel to completely cover the zip and press and topstitch on place so the zip is covered by a fold of fabric.

Then I make sure the two peices sewn together with the zip closed are the same size as the front panel of fabric. I the open the zip, put the front and back pieces of cushion togehter (right sides facing) add the piping and pin all around. Then I sew around all the edges, zigzag and trim the seams, turn the cushion cover right side out through the zip opening, and viola, you have a lovely cushion cover with a hidden zip.

You can get by without a zipper foot but be very careful to manouver the zipper pull so it doesn't end up under the foot. Just sew halfway, with the zip closed, then, with the needle down and holding the fabric in place, lift the foot up and open the zip so the zipper pull is behind the foot, then lower the foot and continue sewing.

You don't need basting stich, but you can use the biggest stictch you have for the topstitching, it looks better.

It is really simple, just as you describe, but taking heed of OMDBs point on sewing around the zip pull

& you can even make cushions easier still, & not bother with the zip at all, use filling such as poly beads, so you can just wash the whole thing in one go, without removing the covers

Thank you, everyone. Never thought about washing the cushion with the filling! Need to put zip in seam according to my design, but I see the point of not doing so now. Next time. Thanks for zipper foot tip - so obvious but I wouldn't have thought of it!