Seems to fit the bill.

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Note added at 10 mins (2022-02-21 10:07:48 GMT)
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slightly different context, but same idea:

"How can I cover a concrete patio?

To cover a concrete deck with paver, scrub the edge first before laying an even sand path, lay the pavers and trim the edge. Before watering your patio, scrub the edges with a stiff bristle brush and concrete cleaner."

(https://howtodiscuss.com/t/concrete-patio-designs/149195 )

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Note added at 17 mins (2022-02-21 10:14:54 GMT)
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"sand course" might be even better

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Note added at 18 mins (2022-02-21 10:16:04 GMT)
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a.k.a. "bedding sand course"

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Note added at 21 mins (2022-02-21 10:19:07 GMT)
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see e.g.: https://www.bolduc.ca/docs/others/Tech Spec 15 - A Guide for...

"The screeded bedding sand course should not be damaged prior to installation of the pavers. Types of damage can include saturation,
displacement, segregation or consolidation. The sand may require replacement should these types of damage occur. Installation of
the concrete pavers starts with securing string lines, laser lines or snapping chalk lines on the bedding course."

see also

https://www.concreteconstruction.net/how-to/site-prep/site-p...

https://www.pavingexpert.com/layflag3


apparently it's also called a 'laying course':
Nowadays, the bedding used for flags/slabs is more correctly known as the "Laying Course" but many contractors and even a few engineers still refer to it as the bedding

The laying course should be a washed course grit sand complying with the requirements of Tables D1 & D2 of annex D of BS 7533 Part 3.

This should be 40mm in thickness after final compaction.

Pay particular attention to the setting of the bedding course, as the finished surface of the paving will mirror this layer. Ensure correct falls are maintained. Use screeding rails to ensure a correct surface level.

This can be laid either partial pre-compaction or compacted after laying.

https://www.roadstone.ie/product/laying-course/

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Note added at 31 Min. (2022-02-21 10:29:11 GMT)
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https://www.simplypaving.com/products/building-materials/lay...