If the temps are cold, bring the nestbox indoors and take it out once a day for the doe to nurse the babies. An empty copy paper box is useful to put the nestbox in when it’s in the house. If babies wander out of the nestbox, they are contained, whether in the house or in transit. Especially when they get a bit older and “popcorn” around anticipating their visit to mama. I bring the box out each morning. Most always the doe will jump right in, eager to nurse them. You get a good night’s sleep not worrying about them!
I check the nestbox every day in case it gets soiled or a baby dies. Make sure they are warm enough, all together in one spot and well covered. Around when their eyes are opening, you can clean the box if it feels damp or has an odor. Keep out clean fur and hay to try to recreate their nest just as it was before you removed the soiled shavings. The babies never appreciate our efforts and may try to spill over the sides when first put back in the clean nestbox. Put some fresh shavings in the sunshine to warm them. If you can make it much like it was and warm, they’ll settle back in quicker.
When the babies first start to tumble out of the box on their own, turn the box around so the low end is accessible. To give them a “boost” you can place a brick in front of the low end for a step. The nestbox may be removed when the babies are 3-5 weeks old. When I find them spending as much time outside the box as in, I take it out. I put a pile of hay in the same corner the nestbox was previously in. This way they have a familiar soft place to nurse and sleep and better footing on the wire for their small feet.
Best of luck with your litters!