There are several methods of in-ground veggie storage ranging in very simple to quite extravagant if there is such a thing in the root cellaring world.
One of the easiest methods is- At the end of the growing season, bend over the tops so that root energy will not continue to be sent to them. Do not cut the tops off as this will provide entry for bacteria and insects which may destroy the root before you come back for it. Cover the rows with a mulch of straw, hay, or cut weeds and long grass so that the ground is less likely to freeze.
The next easiest option is to make a simple dug out pit. Roots, tubers, and bulb vegetables require little effort to store. Some vegetables - including beets, carrots, parsnips, rutabagas, and turnips - Cover with a 1-2 foot (30-60 cm) layer of mulch such as straw or hay, which will trap air and won't become saturated with water, an easy way of storing vegetables. You can also use wood chips or leaves if you remove them before they decompose in the spring.
Here is a simple cone pit-A cone-shaped pit can be constructed to store small amounts of vegetables such as potatoes, carrots, beets turnips, salsify, parsnips, and cabbage Such structures can also be used for storing winter apples and pears.(fruit should not be stored with veg.)
Another version of a dug out pit uses either a barrel baskets garbage cans and old tubs of some sort. The picture below pretty much explains how to make any of these . Simply modify as needed.
The upside of in-ground storage is that it's easy. The down side is Produce stored in this type of manner must all be removed once the pit is opened during cold weather, particularly when the soil is frozen. For this reason, it is better to construct several small pits rather than one large one. When constructing small pits, place a small quantity of several different vegetables in each pit. Then you need open only one pit to get a variety of vegetables. When several vegetables are stored in the same pit, separate them with straws or leaves.
Here is yet another method of a storage pit. Seems like an awful lot of work for what it is but neat none the less.
A storage mound is yet another simple storage method for crops. A storage mound is similar to the unlined pit but above ground. It is used where groundwater is a problem or where only a short storage period under mild temperatures is anticipated. The vegetables are piled on a layer of straw on top of the ground. The mound then is covered with a layer of straw that is held in place by a layer of soil. The mound usually contains one or two bushels of mixed roots, so when the mounds are removed, all the produce can be taken into the house.