Here's a good video series by 'rcFoamFighters' for beginners learning to work with foam.
They show step by step how to scratch build a delta flying wing with a KFm4 airfoil.
Phase 1a:
http://www.youtube.com/watch?v=C_r2v_SSXK8&feature=player_detailpage
Phase 1b:
http://www.youtube.com/watch?v=oPvZwBR69V0&feature=player_detailpage
Phase 1c:
http://www.youtube.com/watch?v=gJWkqDur-TM&feature=player_detailpage
Phase 1d:
http://www.youtube.com/watch?v=C2LCh7WKo1s&feature=player_detailpage
Phase 1e:
http://www.youtube.com/watch?v=AaeSc3KZqhQ&feature=player_detailpage
Phase 1f:
http://www.youtube.com/watch?v=bilRdvPQCHk&feature=player_detailpage
Phase 1g:
http://www.youtube.com/watch?v=BDH99h4KkWI&feature=player_detailpage
Phase 1h:
http://www.youtube.com/watch?v=uqQ-15vSbeg&feature=player_detailpage
Phase 1i:
http://www.youtube.com/watch?v=2DRkEgS_bX8&feature=player_detailpage
Phase 1j:
http://www.youtube.com/watch?v=v1ECuoc7gBc&feature=player_detailpage
Phase 1 completion:
http://www.youtube.com/watch?v=SepTs2jYFH4&feature=player_detailpage
Phase 2a:
http://www.youtube.com/watch?v=0O-up3Ncopk&feature=player_detailpage
Phase 2b:
http://www.youtube.com/watch?v=a9zBifZ4xEo&feature=player_detailpage
Phase 2 completion:
http://www.youtube.com/watch?v=oClwDXnpskc&feature=player_detailpage
Phase 3:
http://www.youtube.com/watch?v=vi3zjmLjlg8&feature=player_detailpage
First test flights:
http://www.youtube.com/watch?feature=player_detailpage&v=1P3UpAtMtzE
Test and Tune mods 1:
http://www.youtube.com/watch?v=wS7na4sPQ3Y&feature=player_detailpage
Test and Tune mods 1 contd.:
http://www.youtube.com/watch?v=hNH2fpAIXNo&feature=player_detailpage
Changes:
http://www.youtube.com/watch?v=9LFh_fO3KPc&feature=player_detailpage
The comparison plane:
http://www.youtube.com/watch?v=S1HWOqNJIJs&feature=player_detailpage
Very cool...