For me, any stool that has the lil foot rest bars works great. Bonus points if it swivels too, there was a brand of one I used in a guitar shop years ago but I can't remember
but anyway, that way I can find a comfortable position to rest the guitar on my lap so it's not sloped all weird, and I can make adjustments as needed. Though, even an office style stool on wheels will work, I use one currently and just find a box or something to rest my feet on. Just... Anything without arms, or as mentioned above, a chair with collapsible arms