Mix the water and the quick-setting moulding powder according to the instructions. Place a layer of the mixture on the bottom of the jar, not thicker than 1 cm.
Wait for the moulding paste to harden (approx. 20 min), then add a layer of 1.5 cm of gravel.
With a large awl make two holes in the thin plastic circle. Push the two straw sections through the holes, letting them stick out a bit the other side. Push the straws into the gravel layer.
Prepare some more moulding paste and fill the rest of the jar almost to the top. Wait for it to set, then decorate the surface to create a small landscape.
Punch a hole in the center of the bottle cap and push through one of the flexible tubes for about 2cm. Seal on both sides with hot glue.
With transparent adhesive tape, stick one thermochromic strip on the bottle and the other one on the small glass.
Download the diagram below from the Blueprints/Plans section and cover it both sides with transparent plastic sheet or laminate it. Cut out the outline.
Open the cardboard ring by cutting it vertically.
To make it waterproof, cover it with plastic sheeting or laminate it
With double-sided adhesive tape, fix the ring inside the diagram to form a cylinder. Staple both ends to fix it well.