Complex arrangements, such as curved bays or windows with radiators tucked beneath, call for clever solutions. It all comes down to carpentry. For a bay window without right angles, that means following the curve. To do this with stock cabinets or DIY boxes, arrange units side by side so that just their faces meet at the corners, like a hinged toy snake. Cut a plywood top that matches the contour and covers the gaps between the units at the rear. Be sure to fully support the seat from below and behind. For a perfect fit and for a large bay, such as the turret-style one shown above, go the custom route. This will push the $3,000 envelope, but rest assured that the built-in will add value, especially if you integrate storage.