In between Geilo and Hagafoss (next to road 7 towards Oslo) is an area called Kvisla. There is a parking from where you can come to some of the cross-country trails in between Geilo and Hol.
Drive towards Oslo from Geilo. Turn left Hagesetvegen. Continue uphill from this road to the right Hingsavegen and the parking lot will be on the right. The cross-country trails on the other side of the road from the parking lot.