Interestingly enough you cannot import Drawings as pictures in Writer documents. (I assume that is because it would make the Open Document file format much more complex.)
However, you can export Drawings to another standard document format like SVG (Scalable Vector Graphics) and import the exported .svg files into Writer documents. I suggest to put every diagram or page in a separate Drawing (instead of using slides inside one Drawing) to make exporting easier.
To insert pictures that have the size of a page, you should insert a manual page break at the end of the page that goes before the page to be inserted and (create and) use a page style that has the correct orientation, headers and footers, and margins (and possibly other properties).
Make sure you keep the original Drawing files to make changes later. If you create a chart in your Drawing, with custom values in the data table, you can only change those values in the Drawing document, not in an exported SVG files (as they only store the graphics - rectangles, colours, lines, text, etc. - not the data table).