I found Hemlock around late August, and he was the last critter I collected in prime decomposing time. I thought he would be the last, anyway. He was a fairly large squirrel in decent shape, so I was excited to have another undamaged skull.
Have you ever seen a dead thing look so cute?
Here is how I wrap animals for decomposition: First I put down a layer of plastic mesh with a small cutting of tulle on top. I wrap the animal in tulle, taking the ends and using a bagtie to tie them together like a little bindle. This layer of mesh fabric will keep all the smallest bones together and prevent anything from getting lost while the animal decomposes, but small bugs can still make their way inside to feed on the soft tissue. This is my favorite method and works without flaw every time.
Then I close the plastic fencing around the body and bagtie it closed. I use as least enough bagties to ensure that other animals cannot break into the plastic or reach their little hands in to tug at the tulle and animal. I have lost many small animals like mice to hungry raccoons who will pull them right out if they can get their hands through, so make sure it's sealed well.
With your tulle and plastic mesh nice and secure, you can put your critter in a good hidden place to decompose. Do not bury it under dirt. You want to sit it right on the surface of the soil. If there are leaves, rake the leaves back so the bare soil is exposed. I do this in my backyard, but if you don't have a good place or your own property to do it, you may be able to find a secluded spot in nearby woods. This may make it more vulnerable to hungry wild animals, but putting some sticks and branches on top, or stabbing some sticks through the holes in the fencing to keep it in place will deter them enough. Also be careful to chose a place with little human traffic. Always be careful for your own safety and considerate of others.
Some people may worry about the smell, but I find you cannot smell it unless you are standing a few feet away. When your critter is on the ground and covered in a thin layer of leaf litter, the smell doesn't travel very far. Plus, with fairly small animals, they just don't produce a ton of smells. I almost never notice the smell when I'm in my backyard unless I am actually inspecting the progress of decomposition.