Sale order with box but no quantity or a variant

I have one problem with the sales order
i need to take the sale order without variant just boxes

example let assume that I have 3 product
1 groundnut oil, 2 sunflower oil, 3 fresh oil
in this, I have variants like 1/2 liter pack, 1 liter, 5-liter tin, 15-liter tin, and all variants are same in all products

my customer will give order buy boxes
they will say groundnut 500 boxes, sunflower oil 250 boxes, like this
when I want to delivery order then they will confirm the variant of product for commented boxes
and the invoice sales price for the product will be at the time sale order commented date
anyone can give the idea to customize.