I am currently planning a kind of bean bag in snail form (see attached image) but however, still have enormous problems with the sewing pattern

Note that the bottom is not intended to be round, but rectangular below and the top, as in the picture, roundish (ie quasi a cross-sectioned cylinder with cuboid bottom).
The whole is sewn in a typical tablecloth fabric, so from a type of plastic. The Beanbag would be around 70cm high and the total size will be approximately 4x4 meters.
Can anybody help me ?? I am really getting more and more desperate

Greetings, Kalliope