The Back Channel (裏のチャンネル Ura no Channeru) is an alternate realm between the physical world and the World of Souls, and time and space work differently there. However unlike the World of Souls, time still flows in the Back Channel, thus allowing living beings to enter it without repercussions.
Entering Back ChannelEdit
There are several ways to enter the Back Channel.
Entry into the Back Channel is no simple task itself as normal individuals cannot even detect it. The mystery behind the Back Channel lies in the fact that it was a spatial anomaly created by ANOTHER, resulting in its few entrances being impossible to find.
By eating PAIR, one can see through the Back Channel and even enter it, as well as see and communicate with Food Spirits, as PAIR's second half falls within the Back Channel. However, if one eats NEWS, they can even create Back Channel space and enter it wherever they desire, by making their cell division speed surpass the speed of light.
There are several ways one can use Back Channel. Apart from communicating with the Food Spirits, one can use the Back Channel to alter space or time.
Both of these applications most likely require the user to have consumed NEWS.
Warp Road is the spatial utilization of Back Channel.
The user finds, or creates rips into the Back Channel, links two areas together for extremely safe travel outside of the physical world. It is unknown if one actually has to travel inside the Warp Road, or if it functions like a portal, with the latter being the most probable one.
Entering Warp Road allows for extreme stealthiness, as shown by slipping through the Back Channel without any trace, leaving next to no scent. It is a space that can be used in order to safely travel through the Gourmet World without any form of repercussions.
Warp Kitchen, later in the story just simply referred to as "Back Channel" is he temporal utilization of Back Channel.
The user creates a space where time flows differently. According to Joie, the space is a memory of Gourmet Cells, and exists to compensate for immense preparation time of some ingredients. 
In the NEWS Warp Kitchen, one perceives as if time was flowing slower. One minute on the outside can seem as days inside. Warp Kitchens created by powerful individuals can have such a slow flow of time, that it almost seems to completely stop. This kind of Back Channel is also most notably found in the Seven Beasts, where the Warp Kitchen was produced directly by ANOTHER, and produces time dislocation of up to 1 to 360.
Also, Warp Kitchen is not necessarily fixed to a point on space, and can be used as a coat to vastly increase travel speed. When inside of this Warp Kitchen, one ages at the normal pace. For example, spending 1 year inside Pandora will only age you by 1 day.
In the Deer King's Warp Kitchen, on the other hand, one perceives the time passage at normal pace, except that they age extremely fast. For their consciousness, only seconds may pass by, but their body will age by years.