We did this last year for our son, and it got lots of compliments.
I had some old flannel shirts, so I started by cutting squares out of them and using fabric glue to put them on like pathes onto his bibs and shirt. I used a green button down shirt, but a flannel would work too.
I also got some fake fall leaves and tan felt sheets from the craft store. I used a hot glue gun and glued the leaves onto his shirt and bibs also. I managed to find a straw hat at the store, and glued the leaves to that too.
I used the tan felt sheets and cut them so they looked like straw. I used fabric glue and glued the felt at the end of his sleeves and pants, and around his collar. I also glued some of it under his hat, to make it look like his straw hair.
Since I began to get carried away, I ended up going back and buying some black and orange felt sheets, some orange pipe cleaners, and some of those google eye things. I ended up cutting out a pumpking and glued that to his bibs on the pocket. I cut out a crow, sewed it together 3/4ths of the way, stuffed it with cotton, shoved the pipe cleaners in there for legs, and sewed the rest of it up. Put the ggole eyes on it, and attached it to his hat. That was fairly simple, cause it was a straw hat, and the crow pretty much stuck on there with just the pipe cleaners shoved in and hooked under.
