A_Drust;
The type of haystack you are looking to "build" would actually be a mound of cuttings in a heap. As such the easiest way to model this is.
1. Find a styrofoam half-sphere (Check dried flower arrangement section of Wal Mart)
2. Secure on to the groundwork with Elmers or similar water based glue
3. Over spray the entire thing with a dark brown or black.
4. Cover with a diluted mix of water and white glue
5. Attach "hay" can be cut from brush bristles or I use cheap doll makers hair (Wal Mart again in the craft section)
6. Attach "hay" in layers and secure each layer on top of the other until you reach the desired look.
7. Overspray lightly with deep yellow to start
8. Overspray lightly with light yellow next
9. Dry- Brush with a lighter mix
10. Overspray with a Dull-Cote Spray (Testors etc.)
Have fun. It works out really well and quite quickly.
Cheers;
Gregory