You can create any size of flex banner through stitching. However standard sizes without seaming are 6ft width by any length and 10ft width by any length. Because the flex material comes in large rolls of 6ft and 10ft widths, you can print as much as the roll allows without seaming. For widths taller than 10ft, you would need to print on more than one rolls of flex material and then stitch them together.
Flex banners are relatively easy to install once their edges are seamed and eyelets installed. They can be installed on walls or fences easily using ropes or better still, cable ties. For more professional installations, tension screws are used to install them on frames. This is the method used in billboards and more permanent installations.
Design for flex banners is done by first working out the physical size and designing for a smaller ratio of that size in high resolution if working in a bitmap format. For vector formats, you can simply workout the size ratio and design in any size. Vectors are best for flex banners because the produce clearer prints with a very small file size.
The price of flex banners is determnied by their size. Typically the price is calculated in square meters.