I've made mine with pondliner. Dug a hole about 0,90 meter deep, added 0,10 m clean (no sharps) sand and placed pondliner on it. To keep it level i used a woden rail ( 0,10 m high and 0,01 m thick) and i put some electrical pvcpipe (about 0,01 m in diameter) fileld with mos to keep it open trough teh liner just under the wood yo keep it from getting to wet. Then i filled in with finnpeat : clean sand 2: 1.
I've been growing most sarraceniaspecies, D. rotundifolia, intermedia, anglica, filiformis, binata and P. vulgaris and grandiflora very succesfully in it.
It is most of the time possible to walk on it (i have to, it's 25 square meters).
If you want raised beds, You can make boxes of wood any shape and hight you want en use the same liner and infill. Be carefull though, a raised bed dries out faster (wind e.a.)!
Marcel