/s/ Blends

In order to produce the /st/ sound, make the hissy snake sound (i.e., /s/) up your left forearm with your right index finger. When you get to your elbow, make the /t/ sound.

In order to produce the /sp/ sound, make the hissy snake sound (i.e., /s/) up your left forearm with your right index finger. When you get to your elbow, make the /p/ sound.
In order to produce the /sm/ sound, make the hissy snake sound (i.e., /s/) up your left forearm with your right index finger. When you get to your elbow, make the /m/ sound.

In order to produce the /sp/ sound, make the hissy snake sound (i.e., /s/) up your left forearm with your right index finger. When you get to your elbow, make the /p/ sound.