This wedding arch flowers tutorial is more intended to show the construction and attachment of florist foam to the structure and explains how using greenery to quickly turn an expensive "solid mass of flowers" into an affordable swag of flowers wired individually onto the metal arch.
Swags are designed individually and then transported to the site and wired onto the arch. Although this swag is VERTICAL - the same design can be created HORIZONTALLY - placing it at the top of the arch instead of the sides.
Lovely photos of hundreds of flowers massed on arches and chuppahs are widely found everywhere on the internet. They are fairly easy and very doable by even a novice, but be warned however that is is very easy to insert $100 worth of flowers in a single yard of foam. For those who want a lovely backdrop that is a little more affordable, common greens are easy to use and can stretch that flower budget considerably.
So I urge you not to look at this as a "gladiolus" tutorial - but rather a quick lesson in structure that can have a changed look completely by using other flower/greenery choices, including roses, alstroemeria, daisies, sunflowers, and dozens of other great selections.
If this is to be a summer outdoor wedding, take care to choose flowers that can hold up to the task. Thirsty flowers like hydrangeas or Gerbera daisies sometimes have to be attached just a short time before the ceremony if held outdoors with substantial heat issues. If time does not allow you this luxury, choose flowers that can be constructed up ahead of time and will still be fresh when the ceremony time comes around. Don't forget to mist well with a flower sealant and keep it on hand for a few quick spritzes before the guests take their seats.