Recently , I am looking for a standing desk for myself.
I first look it up on amazon/ebay/walmart , I find that those well made and so called "ergonomics" standing desks , are really really expensive.
So I switch to a custom standing desk to save some money (for my boss , more exactly)
Refer to this article "A standing desk for $22" , it's a good start.

Basically , you need a desk for monitors , and a shelf for keyboard/mouse , and adjust the height of shelf according to your height 😀 , everything should looks like this picture ( it comes from the article above)

Here are the parts that I used , they are almost the cheapest items I can find in ikea :

Black side table    <==$7.99 ea

Black shelf            <==$1.99 ea

Black bracket      <==$0.50 ea         , you will need at least 2 of this one

Screws that I used ( brought from lowe's)
HillMan Wood Madera Screws #8 1-1/4 in <==$1.79 each bag (8 pcs) HillMan Wood Madera Screws #8 1-1/2 in <==$1.79 each bag (8 pcs) For more than one monitor , you can add more side table. I have triple monitors , then it looks like this

Have fun.