why not let the water trickle over along the entire border between the bog and pond. much more realistic and it will provide current throughout the entire bog area while at the same time keeping the force of the current in any one place low.

like you mention, flat rock directly on top of the liner to hide it. then normal rocks of different shapes and sizes on top of those. No sealer between the flat rocks and normal rocks. the idea being to let the water flow.

I would advise you to put some small fish into your bog area to help control the mosiquito larva.

Yankee Dog

That's pretty much what I'm doing. The inside bog area (excluding the border blocks) ended up 80"x46"x10". It's mostly above grade. Didn't think about the mosquito problem. If I have enough flow through the blocks then there shouldn't be much standing water above the pea gravel which should hopefully prevent mosquitos.

Here are photos of the finished bog. I think it came out pretty good. At first there was too much water leaking through the rock border between the bog and the pond. So I sprayed some waterfall foam into the cracks and that slowed down the leakage enough that water filled to the top of the bog and then slowly flows over the top.

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That is a beautiful setup!