You can use sticky foam pads for a 3D effect or simply glue the toppers to the card base.
6 Flower Barrows Square Card Toppers for Card Making, Journals, Tags, Floral
Wildflower Bouquets Square Card Toppers for Card Making, Journals, Tags, Floral
Paper Flowers Flat Square Card Toppers for Card Making, Journals, Tags, Floral
Boots and Flowers Square Card Toppers for Card Making, Journals, Tags, Scrapbook