A surgeon's knot (double overhand knot) into a loop works fine. Cut the strap in half, add your loop and you've got about a 6' tree strap.
"suspension" refers to all the components to suspend your hammock between 2 trees. "Tree Strap", Hugger, etc. is one component of your suspension.
Speer's original suspension is just 2-15' lengths of strap, one tied to the hammock, the other you tie to 2 trees. A bit more work, as it's hard to adjust. There are MANY options. If you're going cheap, you can get long straps from backwoodsdaydreamer.com, arrowheadequipment.webs.com or many others here... Arrowhead will sew loops for you, as will Jacks are Better... I think Scott at BackwoodsDD will too...