High Hedge Trimming on Uneven Ground

Okay, so I have a high hedge that I take my life in my hands every time I have to trim it. I use a Stihl petrol hedge trimmer, on an extension pole, but the balance is really not great given the extreme height. I prefer to use a shorter reach pole but then I have to teeter on top of a completely inappropriate ladder, rammed into the ground. It's just dangerous all over.
I would like to buy a flat platform that I can stand on, but the ones I can see online that have adjustable legs (to cope with the uneven ground) are not continuously adjustable, so they would not really accommodate the sloping and uneven ground that I have.
Does anybody know of something that might fit the bill?
AMUSING ASIDE: one of the web searches I conducted through Google was the word 'platform' and "continuously adjustable legs" (those three words in inverted commas). This search generates just one hit, and there is NO WAY I'm clicking on the link, as I think from the brief description that they are not talking about trimming a hedge..... well, not a green one!!!! Seriously, I have not clicked on the link (I'm at work) and I STRONGLY ADVICE you do not click on it either unless you have understanding employers!!!!!!!!!
Back to the subject: if anyone knows of a company that might supply an adjustable platform with legs that lock in place at any range of extension, I'd love to hear. Ideally, the platform would enable me to stand about five feet in the air, just to make it challenging.

Crystalclears pic shows what are known as 'Durastilts' or plasterers stilts. Not quite so daft as might first appear - some glasshouse tomato growers and plasterers use them all the time. They come in various heights - Google them. And they do meet risk assessment requirements
But for your purpose I think an ordinary ladder with a piece of 15mm shuttering ply about 2m wide and 0.6m deep strapped horizontally to the back of the top of it would solve your problem, and then you can use an ordinary short reach hedge trimmer rather than an unwieldy long reach one. The ply will spread the load across a large area and stop your ladder sinking into the hedge. And obviously make sure the ladder is suitably levelled with decent purpose made chocks first if you're on uneven ground.
For those that doubt this will work, I have been using exactly this method for the last 25 years to deal with the regular trimming of hedges of Griselinia and Pittosporum which are 3.5 -4m high, and I can trim across the tops of these also quite easily using the same method.

Thanks for those suggestions. I think the plywood board might be challenging: the hedge is a pretty rubbish mix of things (including maple, I think) so it is fairly open construction, and the slope of the ground is quite challenging. The Durastilts look great, but again, I'm not sure I wouldn't end up toppling on the gradient I have. I wonder about investigating aluminium scaffolding poles of some type, and locking fittings. They might turn out to be more expensive, and a phaff, but I am increasingly concerned that I'm not as nimble as I once was (big round number birthday next year). Thanks for the suggestions thus far.

A tripod ladder is the best thing. They are available either with one adjustable legs or all 3. They are very stable even at significant height. I cut hedges up to about 20ft high with 14ft one. I can use it comfortably on very uneven ground.

Henchman platforms are good but much more cumbersome and heavy to move around and set up.