This is a pretty gruesome image and also a bit cartoonish. When we think of punji sticks we, at least I, think of a sort of cartoon pit or giant tiger trap that something will fall into and get spiked on. Actually, punji sticks can and have been used to great effect to slow down or stop an enemy. If you’re not too squeamish, do a Google image search and check out some of the shallow punji stick pits you find there.
One trouble with setting up punji sticks is making sure people in your own group don’t get snared in them. It’s more than likely that zombies wouldn’t think to avoid them but it’s certainly possible. There’s also the question of being attacked by other groups of survivors or wandering individual survivors. The simplest form, MUCH less dramatic than the pikes I’ve illustrated here would be a simple board with nails in it. Dig a shallow pit, put a wide panel at the bottom with nails sticking up and cover it with leaves. Just remember where it is and it will at least slow down an advancing walker, hopefully tripping them up.
For simple defense, the punji sticks are a big plus. One other thing you might try though I haven’t illustrated it yet would be piles of rounded rocks. If you’ve ever walked in a stream or river bed you know it can be a bit tough scrambling over piles of loose rounded stones. Zombies would have the same problem. So throw a nice ring of loose stones around your place to help slow them up and you’re off to a good start.