So I got this dog basket ages ago and he's never been keen on it. It came with a 2 inch thick pad - if you can call it that. I had changed it to a foam cushion from our old couch, but that was still too firm for him, although it was handy for the midget to look out the window!
I had old pillows to use up rather than bin, so after washing and battering to get fluffed up and sort of even again, I found that it fits as is. So that made life very easy. With the fabric scraps from my stash I made a pillow slip, handy that the twill bit was already cut to size. I used the left over fleece for the top part, because it's soft and cosy and he loves fleecy blankets.
Ten minutes later we have a comfy bed, that he actually likes to jump into.......... oh he doesn't sleep there, he's such a cling-on and lives the good life on the sofa/bed