The Belgian site of the "GR Long distance footpaths" has a section which covers daywalks on GR routes whereby the startpoint is at one trainstation, and the the endpoint is at another trainstation. The distances vary between 18 and 32 km's and you can download the GPS track from their website
Lierde - Munkzwalm
Part of the Flemish Ardennes, you are walking in a rolling landscape and along the borders of the river Zwalm. Majority is via slow roads, small forest paths or along fields.
Just leaving the trainstation in Lierde, you are passing an artisanal bakery "de broden van Liesbet". Liesbet, the baker, is doing all the baking in full view and specialises in sourdough bread. As Lierde is not far away from Geraardsbergen, they also have their own made "Mattetaarten", a speciality of the region.