If you have considered a standing desk and tried out solutions with cardboard boxes or breeze blocks and found then wanting then the next thing to try might be this Ikea hack. The hack takes a desk and puts it on its side using a bookcase and a with a few L brackets you have a stable standing desk.
The desk is notable because of its relatively low cost and easy assembly and also because it provides equal size desk areas for seated or standing use. In addition the total floor area it takes up is surprisingly low.
The build’s designer Josh Newman lists all the parts and possible changes that can be made along with complete build instructions at IkeaHacker