Parish

Slaidburn
genuki Slaidburn has useful information about the parish.
In particular under maps the one showing parish boundaries is an old map showing the old names.
You can enlarge the view so it is possible to read the names.
Near the green number 280, there is the name Old Ing which might be relevant to John Willis eldest son of Henry. It is near Easington. Close by is Clapham Common and Austwick Common. So if the Willis family lived in this part when they married they were close to Clapham parish. If you scroll to the left you will find Botton Head which I think is where Nicholas Willis was in 1841. Further over to the left near the green number 133 is Over Wyresdale and just below it is Doe Holme the farm where John Remington and Isabella Leech lived, and where Richard and Isabella Slinger ended up.

Clapham
I am slowly slowly making my own transcript of the parish register from findmypast starting with baptisms 1748 - 82. It is in a clear hand and mostly notes residence. Gentry indicated by use of Mr. craftsmen noted, but farmers and agricultural labourers making up the majority no occupation. Some page corners bent hiding part of entries.

Again genuki Clapham has useful information about the parish. The parish boundaries old map shows the village of Clapham near the green number 276. Just to the left you can find Tewit Hall, where Nicholas was born, Green Close and three squares below Dubgarth where Ann was born.
For the Remingtons over to the left going towards Ingleton you can see Yarlsber where our Jane Remington lived with her daughter.

A modern map by googling Slaidburn farms is also useful. If you try Clapham farms it gives you a map of London Clapham. But you can move the Slaidburn round. Tewitt farm is signed twice, on one of them is a photo - do not know if it is the right building but it is stone.

There is a lovely photo of Dubgarth - google Dubgarth Harling (rootsweb website).