Advice on laying railway sleepers for small raised lawn

Hi, I need some advice on using railway sleepers to make a small raised lawn. The area i am going to lay it on is a small trench maybe half a meter wide on the edge of paving stones. I was wondering what way i would go about putting the sleepers on the paving stones themselves. Would it be ok to just set them on the the edge and screw them together or would i need to put to put a layer of cement below them.

 

I kinda figured that railway sleepers are the same thing that we call railroad cross ties. So I hit Wikipedia and sure enough, they are, in fact, one and the same. Here they are made of wood and creosoted. The article mentioned that in Europe and Asia, they are made of pre-stressed concrete, steel and plastic composite.

So what are your railway sleepers made of? The creosote woods ones here are considered hazardous material, but we have a few that we are using for corner posts in the fence. They are also used for retaining walls, landscaping and steps. Because they are treated with such toxic material, I don't use them near food producing plants.

I scored some treated telephone poles some years ago, they stayed in a pile until we moved here. Then I made my poor long suffering husband go get them. We used them when we built my barn, along with lots of other lumber and such that I scrounged up. Saved us $$thousands.

 

Recently the electric company replaced the poles, so I called them. I asked if I could have some of them and the very nice lady told me that if the poles laid there long enough, I could have them. So we took my tractor and my husband's Kawasaki mule and dragged home 3 poles, 40 feet long. Future barn poles for sheep sheds!