for that you have to make a new drawable shape in xml, right click on drawable folder and create new resource file name it "progress_drawable", paste this xml style.
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item android:id="@android:id/background">
<shape>
<solid
android:color="#bababa"/>
<size
android:height="13dp"
android:width="13dp" />
<corners android:radius="7dp" />
</shape>
</item>
<item android:id="@android:id/progress">
<clip>
<shape>
<solid
android:color="@color/colorAccent"/>
<corners android:radius="7dp" />
</shape>
</clip>
</item>
</layer-list>
now apply this drawable to your seekbar, also set android:maxHeight
<SeekBar
android:id="@+id/sb"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:max="10"
android:maxHeight="10dp"
android:minHeight="10dp"
android:progressDrawable="@drawable/progress_drawable"/>