Homemade slackline

I don't feel like buying an expensive slackline system, is there any way I can use a roll of climbing webbing from red, put one sling around each tree, and tie the webbing on carabiners attached to the slings in some way. Maybe an adjustable knot like a clove hitch, but a clove hitch doesn't work with webbing.  Would this work?  What knot would I use?

http://www.instructables.com/id/How-to-Set-Up-a-Slackline/

No need for ratchet, works great. Can use variations, but basically same, loop line underneath previous and tension. 

stolo wrote:

http://www.instructables.com/id/How-to-Set-Up-a-Slackline/

No need for ratchet, works great. Can use variations, but basically same, loop line underneath previous and tension. 

Thanks, whats a good webbing width to use?

I have always used 1 inch. Wider might work for the carabiner/rap ring setup, I have not tried though. 

The clove on the left is supposed to be on the right most side of carabiner - the left side is used as a pulley/to tension the pulley side of slackline, sorry for error in drawing. 

Google "how to rig a primitive slackline." There tons of videos on YouTube and elsewhere that answers your question. Basically you need some 1" webbing, 4 or 5 oval or HMS carabiners and two rap rings.