I have one of these, it's the cheapest i could find that has sides. well made does the job although a bit large, that's only a problem when you loose a small fish in it. lol. http://www.fishingrepublic.net/carp/unhooking-mats-slings/theseus-carp-carp-cradle-tcc.html
How much do you want to spend ,
I would suggest the Shimano total protection mat
https://poingdestres.co.uk/carp/unhooking-mats/shimano-olive-protection-unhooking-mat
I too found triggerlink a waste of time .
Another gimmick .
I am very much in the keep it simple camp .
Location, Bait and bait application is far more important than some over complicated rig.
I am positive that many of these rigs are made by anglers by simply putting all the components they have in a bag giving it a good shake and seeing what comes out the other end!