The dwarven stone bed consists of two parts: The actual bed made of stone, and the covers for it. The stone bed does not need to actually be a "bed" so much as it is a stone slab with runic enchantments engraved into it. It can even just be a flat area of stone still attached to a mountain, so long as the runes are inscribed, making for some high-powered military bunks. The covers are cloth of high quality with runic enchantments woven into them as well. Dwarven cloth being sturdy even at a luxurious level, the covers resist fire, water, mold, even tearing, but can be worked with traditional seamstress's implements. Some covers have clever coloration and stuffing, even internal folds and seems to disguise and camouflage them while in use.
To use the stone bed, the dwarf takes the covers with him as he travels, and when they bunk down for the night, he simply wraps up in the covers and is transported to the stone bed back in safety, for the night. The dwarf's body remains inside the covers, but is turned to stone beneath them, his presence at the bed a "projection" of sorts, of the dwarf's spirit. He doesn't have to stay in the bed, but can actually get up, eat, drink, avail himself of the facilities or company, for the duration of the bed's activity.
After eight hours have past, the dwarf will be transported back from the stone bed to his body, sound and as mobile as ever after a nights rest. If the dwarf is not back in the bed at the end of the duration, his body remains made of stone, and his "projection" becomes a figurine likeness, and will remain as such untill the two are reunited. Another concern is that during the duration, the dwarf is unaware of his stone body, so may wake up with an arm broken off, or in pieces if the stone is shattered while he sleeps. Most dwarves using stone bed are vigilant about setting a reliable watch to avoid the potential nightmare scenario of waking as pebbles. Destruction of the stone bed or the runic enchantments just leads the bed not to function, which could inconvenience a dwarf that didn't have a plan to endure the local evenings climate.