Nail white expansion foam to the inside of the wooden frame. This foam is a spongy material that allows the wall a small amount of movement without any danger of damage — for instance, if materials expand slightly when the temperature changes. Make sure the foam sits centrally on each length of wood (image 1).
Position spacers inside the floor of the wooden frame, ready to hold the glass blocks (image 2). Check that they are level and accurately spaced to fit the dimensions of the blocks. Trowel white mortar onto the frame’s floor, between the spacers. Spread mortar onto one side of a glass block. Try not to get any on the block’s face (image 3).
Place the first block onto the spacers, pressing the mortared side firmly into position against the frame and bedding the block into the mortar along the floor (image 4). Lay more blocks and spacers to finish the row, checking that they are level (image 5). Wipe off any excess mortar with a damp sponge; dried mortar is hard to remove from glass.