Andrew and Jahaira from Good Dogz KC share their go-to custom slip leash.
"The "Good Dogz KC Indoor Slip Tabs" are short (24", 30" and 36") slip leashes that are perfect for dogs that still need directional guidance while practicing obedience inside the home.  They work great outside as well! Just clip your regular leash to the tab and you are ready to go."  Andrew and Jahaira use 3 different lengths for different sized dogs.  
Please check out Good Dog KC for your boarding and training needs.
The beautiful photos are from Patricia Bordallo Dibidox.