The first step is to ensure that the duvet insert is as same as the cover. If you try to stuff an oversized comfort into the duvet cover, it will create lumpy and uneven fill which will not look smooth or flat on the bed. Moreover, it will be pretty difficult to get the cover on. Again, if you choose an insert which is too small it will slip and slide around inside the cover and the c... https://www.aanyalinen.com/blogs/aanya-blog/can-a-duvet-cover-be-used-on-comforter