My neighbour asked me to make 'girly' a boys bike she was handing down to one of her twin two year old daughters at Christmas...so here is what I did...
First off, I searched the web for tutorials and I found this helpful one here...I started out using this and then kind of ended up doing my own thing as my needs were slightly different. It was being used by a child so would need to be tight and secure but also easily removable for washing.
I followed the blog instructions for cutting the fabric. I won't copy them all out here as it is someone else's tutorial.
I then quilted mine with some wadding to make it slightly more comfy and also stronger and more secure.
Then I put the right sides together and machined around the edges...as per instructions. As you can see in the picture below I hadn't allowed quite enough fabric for the sides because I ended up making the cover slightly bigger than my initial drawing.
So I pulled the sides together, folding the end underneath and I tightly hand sewed right up to the pole. The seat cover can still come off the other way.
I then sewed pink bias tape all around the remaining opening, joining the two ends of the tape at the pole with a bow. I thought trying the fancy way of joining the ends of bias tape in that tight spot might be a bit of a faff. I then added ties at the top. To undo the seat cover you untie the top bow, unfold the flap and slip the seat out.
I also covered the protective padding around the handlebar. I just made a tube out of the spotty fabric and slipped it in.