A collage card with a few materials
Give a collage card one main idea, then let spacing and a few supporting pieces do the work.

Start with one found piece
Choose a paper fragment to carry the design: a color block, a small pattern or your own drawing. Move it around a folded card blank. Centered, low on the page and close to a corner create very different results. Photograph two arrangements if you want to compare them without relying on memory.
Add only a few pieces that have a job. A narrow strip can connect two areas; a quiet background can settle a busy pattern. Avoid trimming everything immediately. Larger loose pieces can still move and overlap, while an offcut trimmed too closely leaves fewer options.
Make the layering order clear
Once the arrangement works, mark discreet pencil reference points. Remove the upper pieces and attach the lowest layer first. Spread adhesive thinly and evenly on its back over clean scrap paper. Replace that scrap as soon as it becomes sticky so adhesive does not transfer to the card front.
Press each piece from the middle toward its edges without rubbing delicate printing. Papers of different thicknesses create small steps. Those are not necessarily a problem, but keep them away from places that must fold or accept handwriting. Let wet joins dry before covering them with another large layer.
Leave room for the message
Close the card and look at it from arm's length. If every element demands equal attention, remove a piece that is still loose rather than adding more details. The inside still needs a quiet writing area. A heavy buildup on the front can also make the card awkward to stand or close.
Everyday paper works well for personal collages, but other people's photographs and illustrations are not automatically available for published or sold designs. Use your own images or material with suitable permission for those uses. Store the dry card flat and check it inside its envelope. A clean edge and enough empty space often do more for a small composition than another decorative layer. Keep a photograph of the arrangement if you want to revisit the idea without making an identical card.