Here are a few baby car seat covers for our rented baby car seat. They are just as simple as possible so no thought is required to slip them in and out. I made them from old pillowcase covers, and they have unwanted batting (2-3 layers), fleece, and a layer of our leftover thermal curtain (which I figure might stop a bit of water leaking through). If I wanted to really make them waterproof I would have used a layer of PUL, hemp, and microfibre inside, but I wanted to recycle what I had on hand in the house for free if possible. I'll keep the spares in the car to use if a nappy leaks while we are out and about.