Fuse them with fusible web / vliesofix. Remove the paper afterwards.
Put the pieces on top of eachother
Now, don't move your pieces, and start cutting 1,5 cm (about 0,55 inch) both layers at the same time:
Voila, your 3D paintsplash is visible.
A TECHNIQUE DRIVEN Blog dedicated to mastery of surface design techniques. First we dye, overdye, paint, stitch, resist, tie, fold, silk screen, stamp, thermofax, batik, bejewel, stretch, shrink, sprinkle, Smooch, fuse, slice, dice, AND then we set it on fire using a variety of heat tools.