Tension-stabilized furniture structures and frame assemblies to form simplified flat packing furniture that eliminates all fasteners, welds and braces. Simplified assembly of pre-tensioned structures providing improved stability, uniformity of support and visual aesthetics. The seat cover material can be netting, fibrous material or textiles. The seating system includes outwardly angled side rails having the profile of furniture, such as seats, couches, chaise lounges, ottomans and the like. The angling of the side rails secures their connection to supporting cross rails with the application of a fitted cover sleeve. The sleeves slidingly engage the frame assembly and provide tension to the frame assembly resulting in highly stable furniture.