There are just not enough good slab climbing in Finland, especially with good rock quality. Luckily there are some small places that fit into that category like taivaskallio and munkkivuori which has one really nice slab wall. But Finland has never been slab kingdom by any means, not even close. Pihlajanmäki has also quite a lot of slab climbing, but the rock quality there is not something to brag about.
If you fancy a place with easy and fast access, dries quickly, is child friendly and can be accessed by child carriage, a place that has good rock quality, a place with perfect Fontainebleau mantel topout simulation. Then Pukinmäki (puksun fontsu) crag is just the place for you. By Fontainebleau mantel topout simulation I mean just that. This place is quite unique in Helsinki area and the way the slab ends. It is perfect shoulder training which is really close the way you topout most routes in magical Fontainebleau.
The only downside for this place is that it resides next to road and there are direct view from nearby households to the wall. So if you want to be in a place where you can be completely alone and where you don't meet other people, I'm afraid this place is not for you.