If you are talking about the pin cushion filling, my pattern called for a "subway" tile (a 3x6 tile) as a base. Cover the tile with fabric with 1 side of a velcro strip. Then make your pin cushion and put the other side of the velcro strip on it. Then you can fill your pin cushion with whatever you want (I use crushed walnut shells in mine). If I make another one, I think I'll use the 4x4 square tile instead of the rectangular one.
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If you are going to use sand, I'd suggest lining your pin cushion with a fusible interfacing before sewing it